Process for the preparation of tetrabromobisphenol-A

ABSTRACT

This invention relates, inter alia, to a process for the production of tetrabromobisphenol-A by the bromination of bisphenol-A and/or underbrominated bisphenol-A, which process features: a water and water-miscible organic solvent reaction medium; a relatively high reaction temperature; and the presence, in the reaction medium, of both (i) excess unreacted Br2 during the feed of bis-phenol-A to the reactor, and (ii) sufficient HBr to protect the tetrabromobisphenol-A produced against undesirable color formation. Tetrabromobisphenol-A precipitates from the reaction mass and is easily recovered. Product of high purity (97% or more) and very low color (APHA of 50 or less) can be produced, even when using large excesses of bromine in the reaction.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of commonly-owned U.S.application Ser. Nos. 09/096,332, filed Jun. 11, 1998, and 08/945,158,filed Oct. 21, 1997. Application Ser. No. 09/096,332 is acontinuation-in-part of application Ser. No. 08/945,158, which in turnis a continuation-in-part of commonly-owned application Ser. Nos.08/426,996 and 08/426,998 both filed Apr. 24, 1995 and both nowabandoned. Application Ser. No. 08/426,998 in turn is acontinuation-in-part of commonly-owned application Ser. No. 08/398,837,filed Mar. 6, 1995 and now abandoned. Application Ser. No. 08/945,158 isalso a continuation-in-part of commonly-owned application Ser. No.08/550,044, filed Oct. 30, 1995, now U.S. Pat. No. 5,723,690, issuedMar. 3, 1998, which in turn is a continuation of commonly-ownedapplication Ser. No. 08/426,997, filed Apr. 24, 1995, now U.S. Pat. No.5,527,971, issued Jun. 18, 1996.

OTHER COMMONLY-OWNED COPENDING APPLICATIONS

Other commonly-owned copending U.S. applications relating to preparationof tetrabromobisphenol-A include Application Nos. 09/288,195, filed Apr.8, 1999; 09/407,314, filed Sep. 28, 1999; and 09/416,855, filed Oct. 12,1999.

TECHNICAL FIELD

This invention relates to novel, highly efficient processes for thepreparation of tetrabromobisphenol-A.

BACKGROUND

Tetrabromobisphenol-A is one of the most widely used brominated flameretardants in the world. It is used extensively to provide flameretardancy for styrenic thermoplastics and for some thermoset resins.

Processes used for producing tetrabromobisphenol-A generally fall intothree categories. The first category includes processes in whichsubstantial amounts of methyl bromide are co-produced along with thetetrabromobisphenol-A. Generally, up to 40-50 pounds of methyl bromidecan be expected per 100 pounds of tetrabromobisphenol-A produced. Inmost cases, the processes within this first category feature reactingbisphenol-A and bromine in methanol. The ring-bromination of thebisphenol-A is a substitution reaction which generates one mole of HBrper ring-bromination site. Thus, for the production oftetrabromobisphenol-A, four moles of HBr are generated per mole oftetrabromobisphenol-A produced. The HBr in turn reacts with the methanolsolvent to produce the methyl bromide co-product. After the bisphenol-Aand bromine feed are finished, the reactor contents are cooked for oneto two hours to complete the reaction. At the end of the reaction, wateris added to the reactor contents to precipitate out the desiredtetrabromobisphenol-A product.

The second category of processes features the production oftetrabromobisphenol-A without the co-production of substantial amountsof methyl bromide and without the use of oxidants to convert the HBr toBr₂. See for example U.S. Pat. Nos. 4,990,321; 5,008,469; 5,059,726; and5,138,10. Generally, these processes brominate the bisphenol-A at a lowtemperature, e.g., 0 to 20° C., in the presence of a methanol solventand a specified amount of water. The water and low temperature attenuatethe production of methyl bromide by slowing the reaction betweenmethanol and HBr. The amount of water used, however, is not so large asto cause precipitation of the tetrabromobisphenol-A from the reactionmass during the bromination reaction. Additional water for that purposeis added at the end of the reaction. This type of process typically usesa fairly long aging or cook period after the reactants have all beenfed, and requires additional process time for the final precipitation oftetrabromobisphenol-A via the last water addition.

In the third category are those processes which feature the brominationof bisphenol-A with bromine in the presence of a solvent and,optionally, an oxidant, e.g., H₂O₂, Cl₂, etc. See for example U.S. Pat.No. 3,929,907; U.S. Pat. No. 4,180,684; U.S. Pat. No. 5,068,463 andJapanese 77/034620 B4 77/09/05. The solvent is generally awater-immiscible halogenated organic compound. Water is used in thereaction mass to provide a two-phase system. As the bisphenol-A isbrominated, the tetrabromobisphenol-A is formed in the solvent. Theco-produced HBr is present in the water. When used, the oxidant oxidizesthe HBr to Br₂, which in turn is then available to brominate morebisphenol-A and its under-brominated species. By oxidizing the HBr toBr₂, only about two moles of Br₂ feed are needed per mole of bisphenol-Afed to the reactor. To recover the tetrabromobisphenol-A from thesolvent, the solution is cooled until tetrabromobisphenol-Aprecipitation occurs. The cooling of the solution to recovertetrabromobisphenol-A entails additional expense and process time.

Highly effective process technology for producing tetrabromobisphenol-Ais described in commonly-owned U.S. Pat. Nos. 5,527,971, 5,723,690, and5,847,232, and in commonly-owned co-pending U.S. patent application Ser.Nos. 08/945,158, filed Apr. 18, 1996, 09/096,332, filed Jun. 11, 1998,and 09/149,225, filed Sep. 8, 1998. One of the factors involved inachieving the highly desirable results made possible by thesecommonly-owned processes is relatively close control of the amount ofexcess unreacted bromine in the liquid phase of the reaction mass duringthe bromination. In most cases this amount is maintained in the range ofabout 50 to about 10,000 ppm of unreacted bromine in the liquid phase ofthe reaction mass. Failure to keep the bromine level in the liquid phaseof the reaction mass below this level especially when using a liquidbromine feed can have adverse repercussions, especially on the colorcharacteristics of the tetrabromobisphenol-A product. In commonly-ownedcopending U.S. application Ser. Nos. 08/945,158 and 09/096,332, of whichthe present application is a continuation-in-part, a process isdescribed wherein from about 50 to 20,000 ppm of unreacted bromine canbe maintained in the liquid phase of the reaction mass by employing,inter alia, a feed stream of gaseous bromine to the reaction mass, ifthe feed stream has a Reynold's Number ≧50,000. In this way a producthaving improved color, e.g., an APHA color of less than about 50, andlower ionic content can be produced.

Since the commonly-owned processes referred to above involve formationof tetrabromobisphenol-A precipitate as the bromination is proceeding,such precipitate formation can render colorimetric methods for closelyassessing bromine concentration in the liquid phase of the reaction masssomewhat problematical. And while feed of vaporous bromine in the mannerdescribed in application Ser. Nos. 08/945,158 and 09/096,332, referredto hereinabove, permits greater latitude in the amount of excess brominethat can be tolerated in liquid phase of the reaction mass, it remainsnecessary to observe and maintain careful control over the character(e.g., Reynold's number) and quantities of the vaporous bromine beingfed to the reaction mass in order to ensure production of product ofacceptable color characteristics.

It would thus be of considerable advantage if a way could be found ofproducing tetrabromobisphenol-A of desirable minimal color with processtechnology that is even more tolerant of the amount of unreacted brominein the liquid phase of the reaction mixture. And it would beparticularly desirable if this objective could be achieved withoutsacrifice of other advantageous features of the commonly-ownedtechnology, such as forming during the bromination precipitatedtetrabromobisphenol-A that is highly pure, readily recoverable, andformed in high yield based on the bisphenol-A fed to the reaction. Thisinvention is deemed to make possible the achievement of each of theforegoing objectives.

THE INVENTION

The processes of this invention feature the efficient production ofhigh-quality, low-color tetrabromobisphenol-A in high yields underoperating conditions that do not require such close control of the ratiobetween bromine and bisphenol-A fed into and maintained in the reactionmass. Indeed, it has been found possible to produce low-colortetrabromobisphenol-A pursuant to this invention with as much as about80,000 ppm of unreacted bromine in the liquid phase of the reactionmass. Moreover, the processes of this invention can be run in the batchmode or in the continuous mode. When run in the batch mode, processefficiency is enhanced due to relatively short reactor times as there isno need for a time consuming one hour plus post-reaction cook period ora post-reaction tetrabromobisphenol-A precipitation step. The use of acontinuous process for the production of tetrabromobisphenol-A is ararity in itself and is made possible by the short reaction andtetrabromobisphenol-A precipitation times which are features ofprocesses of this invention. In the continuous mode, reactor size can besubstantially reduced without a loss in product output.

In addition to the above reaction efficiencies, the processes of thisinvention are capable of producing high yields of tetrabromobisphenol-Ain a methanol- or ethanol-based solvent without the substantialconcomitant production of methyl bromide or ethyl bromide, e.g., aslittle as 0.2 to 1.0 lbs (ca. 0.09 to ca. 0.45 kg) of methyl bromide orethyl bromide per 100 lbs (ca. 45.4 kg) of tetrabromobisphenol-Aproduct. Even further, it is possible to obtain high yields of almostpure white tetrabromobisphenol-A even though a substantial excess ofunreacted bromine is present in the reaction mass.

Pursuant to this invention there is provided in one of its embodiments aprocess of producing tetrabromobisphenol-A which comprises:

a) contacting, during a period of time, bromine and a continuous orsubstantially continuous feed of bisphenol-A and/or underbrominatedbisphenol-A in a reaction mass having a temperature within the range offrom about 30° C. to about 100° C. and having a liquid phase comprisedof a water-miscible organic solvent, e.g., methanol or ethanol, andwater, in which liquid phase, tetrabromobisphenol-A is relativelyinsoluble;

b) during all or substantially all of the foregoing period of time,maintaining in the liquid phase of the reaction mass, an amount of HBrwhich will protect the color of the tetrabromobisphenol-A precipitate ind) from being adversely affected by the intentional or unintentionalvariance of the unreacted bromine concentration described in c) to aboveabout 20,000 ppm and up to about 80,000 ppm;

c) during all or substantially all of the foregoing period of time,having in the liquid phase of the reaction mass, a presence of fromabout 50 ppm to about 80,000 ppm unreacted bromine; and

d) during all or substantially all of the foregoing period of time,having tetrabromobisphenol-A precipitate from the reaction mass,normally in a yield of at least about 90% based on the amount ofbisphenol-A and/or underbrominated bisphenol-A fed to the reaction massup to that point in time.

Typically, the amount of HBr in the liquid phase of the reaction massis, on a weight basis, from about 6 to about 50 times, and preferablyfrom about 10 to about 20 times, as much as the maximum amount ofunreacted bromine that is expected to be in the liquid phase of thereaction mass during a). In the specification and claims hereof theweights of HBr and of Br₂ are determined or verified by analysis usingsamples of the liquid phase from which precipitate has been removed.Also, reference to bromine in the liquid phase of the reaction massshould be understood to mean unreacted bromine, as distinguished fromtotal bromine which would include both unreacted and reacted bromine.

The length of the period of time in the process of the above embodimentwill usually depend upon the manner in which the process is beingconducted. For example, if the process is being conducted as a batchprocess without removal of reaction mass or product from the reactorduring the reaction, the period of time will be the relatively shorttime during which the reactants are being brought into contact with eachother in conducting a batch process, e.g., (A) during the timebisphenol-A and/or underbrominated bisphenol-A and excess bromine arebeing charged to and are present in the liquid phase of the reactionmass being formed, and the reactor contents are under and comply withthe conditions specified in a) through d) above so thattetrabromobisphenol-A is being produced and is precipitating, or (B)during the time bisphenol-A and/or underbrominated bisphenol-A is/arebeing charged to the liquid phase of the reaction mass being formed andexcess bromine is present in the liquid phase of the reaction mass beingformed, and the reactor contents are under and comply with theconditions specified in a) through d) above. Situation (B) can arise,for example, when:

1) during the charging of the bisphenol-A and/or underbrominatedbisphenol-A, all of the excess bromine present in the liquid phase ofthe reaction mass being formed is being produced in situ by oxidation ofHBr as described hereinafter, and the reactor contents are under andcomply with the conditions specified in a) through d) above so thattetrabromobisphenol-A is being produced and is precipitating, or

2) during the charging of the bisphenol-A and/or underbrominatedbisphenol-A, part of the excess bromine present in the liquid phase ofthe reaction mass being formed is being produced in situ by oxidation ofHBr and the remainder of the excess amount of bromine is being fed tothe liquid phase of the reaction mass, and the reactor contents areunder and comply with the conditions specified in a) through d) above sothat tetrabromobisphenol-A is being produced and is precipitating, or

3) bromine is present in a heel that is present in the reactor beforethe charging of bisphenol-A and/or underbrominated bisphenol-A isinitiated, and during the time the feed of bisphenol-A and/orunderbrominated bisphenol-A is occurring, the reactor contents arc underand comply with the conditions specified in a) through d) above so thattetrabromobisphenol-A is being produced and is precipitating.

On the other hand, the period of time referred to above in connectionwith the process of this embodiment will be much longer when the processis being conducted on a continuous or semicontinuous basis. Indeed,since the period of time is the time during which the reactants arebeing brought into contact with each other in conducting the process onsuch basis with the reactor contents under and complying with theconditions specified in a) through d) above so thattetrabromobisphenol-A is being produced and is precipitating, theduration of such period of time is largely discretionary. This is so,because with the reactor contents under and complying with theconditions specified in a) through d) above, the reactants are beingbrought into contact with each other during the entire time thebisphenol-A and/or underbrominated bisphenol-A is/are being fed to theliquid phase of the reaction mass while either (A) the entire excess ofbromine is being fed to the liquid phase of the reaction mass, or (B)all or part of the excess of bromine in the liquid phase of the reactionmass is being produced in situ by oxidation of HBr as describedhereinafter. Concurrently, a portion of the reaction mass andprecipitate is being removed from the reaction mass so that the volumeof the contents of the bromination reactor remains more or lessconstant.

In typical, properly conducted batch operations, during at least about80% of the foregoing period of time, and preferably during at leastabout 90% of the foregoing period of time, precipitate is being formedthat (i) typically contains at least about 90 wt %, and preferably atleast about 95 wt % of tetrabromobisphenol-A, and (ii) typically isformed in a yield of at least about 90% based on the amount ofbisphenol-A and/or underbrominated bisphenol-A fed to the liquid phaseof the reaction mass up to that point. In typical, properly conductedcontinuous operations, once steady state operation has been achieved,precipitate is continuously being formed that (i) typically contains atleast about 95 wt % of tetrabromobisphenol-A, and (ii) typically isformed in a substantially continuous yield of at least about 90% basedon the amount of bisphenol-A and/or underbrominated bisphenol-A that hasbeen fed to the liquid phase of the reaction mass.

If bromine is to be generated in situ, this is best accomplished byreaction between a suitable oxidant, preferably hydrogen peroxide, andHBr. Hydrogen peroxide is preferably introduced into the liquid phase ofthe reaction mass in the form of a water-containing solution.

Important features of this invention are that not only is thebromination reaction very rapid especially under preferred temperatureconditions used (from about 50 to about 100° C.), but during all orsubstantially all of the time the reactants (Br₂ and bisphenol-A and/orunderbrominated bisphenol-A) are coming in contact with each other inthe liquid phase of the reaction mass under the specified conditions, aprecipitate is being formed that (i) typically contains at least about90 wt %, and preferably at least about 95 wt % of tetrabromobisphenol-A,and (ii) typically is formed in a yield of at least about 90% based onthe amount of bisphenol-A and/or underbrominated bisphenol-A fed to thereaction mass. Moreover, even though the liquid phase of the reactionmass may contain as much as 80,000 ppm of unreacted bromine, thetetrabromobisphenol-A being produced typically is of low color (e.g., ithas an APHA color of 100 or less, the APHA color being determinable bydissolving 80 grams of the tetrabromobisphenol-A product in 100 mL ofacetone).

Formation of the tetrabromobisphenol-A product as a precipitatefacilitates the recovery of the product, as this can be effected by anyof a variety of physical separation procedures such as draining,decantation, centrifugation, and/or filtration. The fact that theprecipitate enriched in tetrabromobisphenol-A can be rapidly andcontinuously formed is of considerable advantage in that it enables theprocess to be conducted as a continuous process. The precipitateenriched in the desired product can be removed from the reaction masscontinuously or substantially continuously, typically along with aportion of the reaction mass, whereby the volumes of feeds to, andmaterial removed from, the reactor can be kept constant or substantiallyconstant at all times. The presence in the liquid phase of the reactionmass of excess unreacted bromine over and above that required to convertthe bisphenol-A and/or underbrominated bisphenol-A totetrabromobisphenol-A ensures that this desired product is formed inhigh yield without significant contamination by under-brominatedbisphenol-A such as tribromobisphenol-A. And the presence in the liquidphase of the reaction mass of the specified excess quantity of HBrrelative to the unreacted bromine ensures that the tetrabromobisphenol-Aproduct will have little, if any, undesirable color. As indicated above,the conventional wisdom in the art has been to avoid the presence ofexcesses of unreacted bromine above 1 wt % or at most 2 wt % in theliquid phase of the reaction mass in order to avoid color formation inthe tetrabromobisphenol-A product. Yet, the practice of this inventioninvolves deliberately keeping unreacted bromine in the liquid phase inamounts which preferably are up to about 2 wt % but which can reach ashigh as 8% without serious adverse consequences with respect to productcolor. Because of the maintenance in the liquid phase of the reactionmass of a color-protective amount of HBr relative to the targeted amountof unreacted Br₂ to be present in the liquid phase of the reaction mass,it is unnecessary to tightly control the amount of excess unreacted Br₂in the liquid phase of the reaction mass. Thus, in conducting theprocesses of this invention, it is now possible to widely vary thecontent of bromine in the liquid phase, intentionally orunintentionally, without excessive color development in the precipitatedtetrabromobisphenol-A.

Since excess bromine is to be present in the liquid phase in thereactor, the source of the bromine can consist of (i) bromine fed to thereactor in liquid and/or gaseous form or (ii) a combination of brominefed to the reactor in liquid and/or gaseous form plus bromine generatedin situ by oxidation of HBr or (iii) bromine generated in situ byoxidation of HBr. If the source of the bromine is the combination offeed bromine and in situ generated bromine, the source of the HBrsubjected to the in situ oxidation can consist of (a) HBr coproduct fromthe bromination or (b) a combination of HBr coproduct from thebromination plus HBr fed to the reactor. While in theory it may bepossible to use only HBr fed to the reactor as the source of HBrsubjected to the in situ oxidation, this would require segregating thecoproduct HBr from the HBr fed to the reactor. If the source of thebromine is solely in situ generated bromine, HBr is fed into thereaction mass along with a separate feed of oxidant, these feeds beingproportioned to produce and maintain the excess of bromine in the liquidphase of the reaction mass, as well as to maintain an amount of HBrwhich will protect the color of the tetrabromobisphenol-A beingprecipitated from being adversely affected by the intentional orunintentional variance of the unreacted bromine concentration in theliquid phase of the reaction mass to above about 20,000 ppm and up toabout 80,000 ppm.

In the practice of this invention the amount of unreacted brominemaintained in the liquid phase of the reaction mass can be as high asabout 8 wt % (ca. 80,000 ppm), although typically the amount ofunreacted bromine maintained in the liquid phase of the reaction masswill not exceed about 3.5 wt % (ca. 35,000 ppm). Preferably the amountof bromine in the liquid phase of the reaction mass is kept in the rangeof about 50 to about 20,000 parts per million (ppm) during substantiallythe entire bromination period. As can be seen from the foregoing, and asis conventional, all parts referred to in any portion of this documentare by weight unless otherwise expressly indicated. And it will beunderstood that the amount of unreacted bromine in the liquid phase ofthe reaction mass is the total of unreacted (free) bromine in suchliquid phase that originated directly from the bromine fed to thereactor, and any unreacted (free) bromine that may be generated in situin such liquid phase by oxidation of coproduct HBr formed in thebromination, if such oxidation is employed in the process.

In accordance with another embodiment of this invention,tetrabromobisphenol-A can be produced by a process which comprises:

a) feeding to a reactor, at least bisphenol-A and/or underbrominatedbisphenol-A, bromine, water, and a water-miscible organic solvent, to atleast partially form a reaction mass having a liquid phase containingfrom above about 15 to about 85 wt % water, the wt % being based uponthe amount of water and water-miscible organic solvent in the liquidphase; and

b) during at least a substantial portion of a), (i) providing for thepresence in the liquid phase of the reaction mass of an amount ofunreacted bromine that is in excess over the stoichiometric amounttheoretically required to convert the bisphenol-A and/or underbrominatedbisphenol-A to tetrabromobisphenol-A, and to continuously form duringsubstantially all of the time the feeding in a) is occurring, aprecipitate comprised mainly of tetrabromobisphenol-A, the yield ofprecipitated tetrabromobisphenol-A during substantially all of the timethe feeding in a) is occurring being at least about 90% based on theamount of the bisphenol-A or underbrominated bisphenol-A or combinationthereof fed up to that point in time, and (ii) providing for an amountof HBr in the liquid phase of the reaction mass which will protect thecolor of the tetrabromobisphenol-A precipitate from being adverselyaffected by the intentional or unintentional variance of the unreactedbromine concentration in the liquid phase to a concentration in therange of from above about 20,000 ppm to about 80,000 ppm.

In conducting this embodiment of the invention the temperature of theliquid phase of the reaction mass is typically in the range of about 30to about 100° C. and preferably is a temperature which is within therange of from about 50 to about 100° C. If an oxidant is included in thefeed to the reactor, a portion of the HBr coproduct is oxidized in situto produce additional bromine in the liquid phase of the reaction mass.Thus the amount of oxidant, if used, should be controlled so that theamount of HBr present in the liquid phase of the reaction mass issufficient to protect the tetrabromobisphenol-A against excessive colorformation taking into consideration the maximum amount of unreactedbromine that may be expected to be in the liquid phase during thefeeding of the reactants. If desired, HBr with or without oxidant can beincluded in the feed to the reactor, again provided that the amount ofHBr is sufficient to protect the tetrabromobisphenol-A against excessivecolor development therein.

Also in accordance with this invention, tetrabromobisphenol-A can beproduced by a co-feed process which comprises:

a) co-feeding Br₂ and a solution comprised of bisphenol-A and/orunderbrominated bisphenol-A, water and a water-miscible organic solventto a reactor to at least partially form a reaction mass having a liquidphase and a solids phase, the liquid phase containing water in an amountof from above about 15 to about 85 wt % water, the wt % being based uponthe amount of water and water-miscible organic solvent in the liquidphase, the solids phase comprising predominately a precipitate oftetrabromobisphenol-A;

b) the reaction mass liquid phase containing during all or substantiallyall of the time the co-feeding in a) is taking place, an amount ofunreacted bromine that is in excess over the stoichiometric amounttheoretically required to convert the bisphenol-A and/or underbrominatedbisphenol-A to tetrabromobisphenol-A, such that during substantially allof the time of the co-feeding in a), the tetrabromobisphenol-A is beingproduced in a yield of at least about 90% based on the amount of thebisphenol-A and/or underbrominated bisphenol-A already fed;

c) the reaction mass liquid phase also containing during all orsubstantially all of the time the co-feeding in a) is taking place, anamount of HBr which will protect the color of the tetrabromobisphenol-Aprecipitate from being adversely affected by the intentional orunintentional variance of the unreacted bromine concentration in theliquid phase to a concentration in the range of from above about 20,000ppm to about 80,000 ppm; and

d) periodically or continuously removing tetrabromobisphenol-Aprecipitate from the reactor along with a portion of the reaction massso that the volume of the reaction mass in the reactor remainssubstantially constant.

In this embodiment of the invention it is again preferable to have areaction mass temperature which is within the range of from about 50 toabout 100° C.

In this co-feed process the formation of the reaction mass can best beaccomplished by co-feeding (1) the Br₂ and (2) abisphenol-A/water/solvent solution, or a bisphenol-A and underbrominatedbisphenol-A/water/solvent solution or slurry, or an underbrominatedbisphenol-A/water/solvent solution or slurry. By co-feeding, is meantthat the Br₂ and the solution or slurry feed periods overlap one anotherto at least some extent. (A feed period is that period of time overwhich all of a subject feed is fed to the reactor.) For example, the Br₂feed can be initiated and then followed by the solution or slurry feed,with both feeds thereafter occurring simultaneously until finished.Another example would be that of an initial Br₂ feed followed by acontinuous solution or slurry feed which is accompanied by a continued,but intermittently interrupted or staged, Br₂ feed. Yet another exampleis that of initiating the Br₂ feed followed by the solution or slurryfeed so that the two feeds occur simultaneously until the specifiedamount of Br₂ has been fed. At that point, the solution or slurry feedcontinues alone until it is finished. Other co-feed schemes couldfeature an intermittently interrupted solution or slurry feed, orinitially feeding the solution or slurry into a Br₂ containing reactorfollowed by a combined Br₂ and solution or slurry feed. It is alsopossible to conduct this embodiment such that the Br₂ and the solutionor slurry feeds are, timewise, completely concurrent one with the other.Still other variants include substantially concurrent or completelyconcurrent but separate feeds of (a) Br₂, (b) abisphenol-A/water/solvent solution, and (c) a bisphenol-A andunderbrominated bisphenol-A solution or slurry, or a slurry ofunderbrominated bisphenol-A. Similarly, it is possible, especially in acontinuous mode of operation, to use alternating feeds such as byconcurrently but separately feeding (a) Br₂, and (b) abisphenol-A/water/solvent solution for a certain period of time, andthen switch for a certain period of time to concurrent but separatefeeding of (a) Br₂ and (b) a bisphenol-A and underbrominatedbisphenol-A/water/solvent solution or slurry, or an underbrominatedbisphenol-A/water/solvent slurry. These and still other co-feedingvariants will now be readily apparent to those skilled in the art.

Feeds that do not have some overlap of the Br₂ and solution feed periodsare possible, but will not be generally preferred. For example, all ofthe Br₂ can be fed followed by the solution or slurry feed. However,depending on reaction conditions, such a feed scheme could lead to theformation of undesirable by-products due to the high concentration ofBr₂ which is seen by the initial bisphenol-A and/or underbrominatedbisphenol-A feed. Another scheme, i.e., feeding large amounts ofbisphenol-A and or underbrominated bisphenol-A before feeding Br₂, wouldnot be preferred as it could lead to precipitation of substantialamounts of tribromobisphenol-A.

When carrying out the above co-feed process, whatever the manner ofconducting the feeding, it must be in harmony with the requirements ofsteps b), c) and d) of the co-feed process.

Another embodiment is a process for the production oftetrabromobisphenol-A, which process comprises:

a) feeding to a reactor, bisphenol-A and/or underbrominated bisphenol-A,hydrogen bromide, an HBr oxidant, water, and a water-miscible organicsolvent, to partially form a reaction mass having a liquid phasecontaining in the range of from above about 15 to about 85 wt % water,and typically in the range of about 30 to about 85 wt % water, the wt %being based upon the amount of water and water-miscible organic solventin the liquid phase; and

b) proportioning the feeds in a) such that during at least a substantialportion of the time when both the feeding and the bromination ofbisphenol-A and/or underbrominated bisphenol-A are taking place, thereis present in the liquid phase of the reaction mass (i) an amount ofunreacted bromine that is in excess over the stoichiometric amounttheoretically required to convert the bisphenol-A totetrabromobisphenol-A, and (ii) an amount of HBr which will protect thecolor of the tetrabromobisphenol-A precipitate from being adverselyaffected by the intentional or unintentional variance of the unreactedbromine concentration in the liquid phase to a concentration in therange of from above about 20,000 ppm to about 80,000 ppm, tocontinuously form during substantially all of the time when both thefeeding and the bromination are taking place, a precipitate comprisedmainly of tetrabromobisphenol-A, the yield of precipitatedtetrabromobisphenol-A during substantially all of the time when both thefeeding and the bromination are taking place being at least about 90%based on the amount of the bisphenol-A and/or underbrominatedbisphenol-A fed up to that point in time.

Still another embodiment of this invention is a process for theproduction of tetrabromobisphenol-A, which process comprises:

a) brominating bisphenol-A and/or underbrominated bisphenol-A by feedingbisphenol-A and/or underbrominated bisphenol-A to a reaction mass havinga reaction mass temperature which is in the range of from about 30 toabout 100° C., and having a liquid phase, which liquid phase contains(i) water and a solvent quantity of a water-miscible organic solvent,the water being present in an amount of from about 30 to about 85 wt %,and preferably within the range of about 30 to about 75 wt %, based onthe weight of the water and water-miscible organic solvent in thereaction mass, and (ii) 50 to 80,000 ppm of unreacted Br₂ so that aprecipitate containing at least about 95 wt % of tetrabromobisphenol-Ais being formed substantially continuously during the time such feedingis taking place; and

b) during substantially all of the time the feeding in a) is takingplace, having in the liquid phase of the reaction mass an amount of HBrsufficient to protect the color of the tetrabromobisphenol-A precipitatefrom being adversely affected by the intentional or unintentionalvariance of the unreacted bromine concentration in the liquid phase to aconcentration in the range of from above about 20,000 ppm to about80,000 ppm.

Another embodiment of this invention is a process for the production oftetrabromobisphenol-A, which process comprises:

a) brominating bisphenol-A and/or underbrominated bisphenol-A by feedingbisphenol-A and/or underbrominated bisphenol-A to a reaction mass havinga reaction mass temperature which is in the range of from about 30 toabout 100° C. (preferably in the range of from about 50 to about 100°C., and most preferably in the range of from about 50 to about 80° C.),and having a liquid phase, which liquid phase contains (i) water and asolvent quantity of a water-miscible organic solvent (preferably analcohol having up to 4 carbon atoms, and most preferably methanol,ethanol or a mixture thereof), the water being present in an amount offrom about 30 to about 85 wt %, and preferably in the range of about 30to about 75 wt %, based on the weight of the water and water-miscibleorganic solvent in the reaction mass, and (ii) at least about 50 ppm butno more than about 80,000 ppm (preferably no more than about 35,000 ppm,and most preferably up to about 20,000 ppm), of unreacted Br₂ tocontinuously produce during at least a substantial portion of thefeeding in a), a precipitate enriched in tetrabromobisphenol-A, suchtetrabromobisphenol-A being produced in a yield of at least about 90%based on the amount of bisphenol-A and/or underbrominated bisphenol-Aalready fed to the reaction mass;

b) during at least a substantial portion of the feeding in a), having inthe liquid phase of the reaction mass an amount of HBr sufficient toprotect the color of the tetrabromobisphenol-A precipitate from beingadversely affected by the intentional or unintentional variance of theunreacted bromine concentration in the liquid phase to a concentrationin the range of from above about 20,000 ppm to about 80,000 ppm; and

c) during at least a substantial portion of the feeding in a),continuously removing at least a portion of the precipitate from thereaction mass.

Typically, the process is conducted such that a precipitate is producedwhich is at least 95 wt % tetrabromobisphenol-A and in a yield which isat least about 90%, based on the amount of bisphenol-A and/orunderbrominated bisphenol-A fed. Also, the tetrabromobisphenol-Aproduced typically has an APHA color of less than about 100, preferably50 or less, the APHA color being determinable by dissolving 80 grams ofthe tetrabromobisphenol-A product in 100 mL of acetone. It is to benoted that if the specified excess of HBr relative to Br₂ in the liquidphase of the reaction mass pursuant to this invention is not utilized,it is desirable to control the amount of unreacted bromine in suchliquid phase to from about 2000 to about 6000 ppm.

In conducting the process of this embodiment it is often desirable toprovide at least a portion of the unreacted Br₂ by the oxidation of HBrto Br₂. This oxidation is preferably conducted by introducing anoxidant, preferably aqueous hydrogen peroxide, into the reaction mass,preferably continuously. However, it is possible, though not preferred,to withdraw, periodically or continuously, a portion of the reactionmass from the bromination reactor, treat the withdrawn portion with theoxidant externally of the bromination reactor in a closed system, andthen return the treated portion of the reaction mass to the brominationreactor. Also, when conducting a process pursuant to this embodiment itis preferred to continuously remove at least a portion of theprecipitate from the reaction mass.

This invention in its various forms referred to above thus provides inessence a process wherein tetrabromobisphenol-A product is produced byproviding a liquid phase reaction system in which there is directlyformed a tetrabromobisphenol-A precipitate by the bromination ofbisphenol-A and/or underbrominated bisphenol-A. The bromination involvesuse of an excess of bromine over the stoichiometric amount theoreticallyrequired to produce tetrabromobisphenol-A. Also, the bromination isconducted in the presence of an amount of HBr that is high enough toprotect the tetrabromobisphenol-A being produced from excessive colordevelopment taking into consideration the maximum amount of unreactedbromine that is targeted or expected to be present in liquid phase ofthe reaction mass during the time the bromine and bisphenol-A and/orunderbrominated bisphenol-A are being brought together in the liquidphase of the reaction mass. Moreover, the bromination is conducted atsuch rate that (i) there is insufficient opportunity for significantprecipitation of the intermediate, tribromobisphenol-A, to occur, and(ii) while the bisphenol-A and/or underbrominated bisphenol-A is/arebeing brought into contact with unreacted bromine in the liquid phase ofthe reaction mass, tetrabromobisphenol-A is being produced substantiallycontinuously. Typically the yield of the tetrabromobisphenol-A as it isbeing produced substantially continuously is at least about 90% based onthe amount of the bisphenol-A and/or underbrominated bisphenol-A alreadyfed. In addition the tetrabromobisphenol-A produced typically has anAPHA color of less than about 100, preferably 50 or less, the APHA colorbeing determinable by dissolving 80 grams of the tetrabromobisphenol-Aproduct in 100 mL of acetone. And when the process is conducted as acontinuous process under preferred constant steady state conditions,where, inter alia, the total volume of uniform feeds to the brominationreactor and the total volume of some reaction mass pluscontinuously-forming precipitate being withdrawn from the reactor arekept substantially constant and substantially equal at all times, (i)the precipitate is continuously produced in a yield of at least about90% based on the amount of bisphenol-A and/or underbrominatedbisphenol-A being fed up to that point in time, (ii) thetetrabromobisphenol-A being continuously produced has an APHA color ofless than about 100, preferably 50 or less, and (iii) the precipitate asit is continuously being formed and withdrawn from the reactor containsat least about 95 wt % tetrabromobisphenol-A.

A further embodiment to this invention is a process for protectingtetrabromobisphenol-A against excessive color development during itsproduction by bromination of bisphenol-A and/or underbrominatedbisphenol-A by bromine, which process comprises:

a) feeding bisphenol-A and/or underbrominated bisphenol-A to a reactionmass having during all or substantially all of the time such feeding istaking place, a liquid phase in which tetrabromobisphenol-A isrelatively insoluble comprising water and a water-miscible organicsolvent;

b) during all or substantially all of the time the feeding in a) istaking place, having in the liquid phase at least about 50 ppm but notmore than about 80,000 ppm of unreacted bromine and having thetemperature in the liquid phase in the range of from about 30 to about100° C.;

c) during all or substantially all of the time the feeding in a) istaking place, having the water and the organic solvent proportioned inthe liquid phase at a weight ratio within the range of from about 30:70to about 85:15 that enables a precipitate containingtetrabromobisphenol-A to be formed substantially continuously duringsubstantially the entire time the feeding in a) is taking place, and ina substantially continuous yield of at least 90% based on the amount ofbisphenol-A and/or underbrominated bisphenol-A already fed in accordancewith a) up to that time; and

d) during all or substantially all of the time the feeding in a) istaking place, maintaining the relative proportions of HBr and Br₂ in theliquid phase of the reaction mass such that there is present therein anamount of HBr relative to the amount of bromine that will protect thecolor of the tetrabromobisphenol-A precipitate from being adverselyaffected by the intentional or unintentional variance of the unreactedbromine concentration in the liquid phase to a concentration in therange of from above about 20,000 ppm to about 80,000 ppm.

Other embodiments and features of the invention will become stillfurther apparent from the ensuing description and appended claims.

Commercially available Br₂ is suitable for use as the Br₂ feed. Shouldthe Br₂ contain undesirable impurities, it can be treated byconventional purification techniques, e.g., distillation, H₂SO₄treatment, etc., which are well known to those skilled in the art.

The Br₂ can be fed as a liquid or as a gas to the reactor. It ispreferred that the feed be gaseous. Whether the Br₂ is liquid orgaseous, it is preferred that the feed entry point be sub-surface of thereaction mass. This is conveniently accomplished by use of a dip tube.If the feed is liquid, above-surface feed must contend with possiblesplattering, bromine loss due to evaporation, and inefficient mixing.

The amount of water in the reaction mass should be within the range offrom above about 15 to about 85 wt %, and typically is in the range ofabout 30 to about 85 wt % of water, based upon the total amount of waterand water-miscible organic solvent in the liquid phase of the reactionmass. Preferably, the amount of water fed is that amount which is withinthe range of from about 30 to about 75 wt % water. Most highly preferredis the range of from about 30 to about 70 wt %. When the water-miscibleorganic solvent is methanol the preferred amount is from about 30 toabout 55 wt %. With ethanol, the preferred amount of water is from about40 wt % to about 65 wt %.

The water content of the reaction mass is an important aspect of thisinvention. It is believed, though the processes of this invention arenot to be limited by any particular theory, that the water contentsuppresses formation of methyl bromide or ethyl bromide and, at the sametime, allows for production of high purity tetrabromobisphenol-Aproduct. Normally, it might be expected that the water content wouldcause under-brominated species, e.g., tribromobisphenol-A, toprecipitate along with the tetrabromobisphenol-A species, therebyyielding an impure product. However, the processes of this invention arein fact capable of producing product of desirable purity as well asproduct with little, if any, color.

In the co-feed process it is convenient and preferred to feed the waterto the reactor as part of a solution or slurry which also containsbisphenol-A and/or underbrominated bisphenol-A and a water-misciblesolvent. However, the water may be introduced into the reaction mass inother equivalent ways. For example, the water can be fed as a separatefeed stream. Such a feed could be essentially contemporaneous with thefeed of a solution or slurry of bisphenol-A and/or underbrominatedbisphenol-A and water-miscible solvent. Even further, a portion, if notall, of the water can be fed as steam or steam condensate along with agaseous Br₂ feed. The steam could have been used to vaporize the Br₂ toform the gaseous feed. Another example features providing water as acharge or as part of a charge to the reactor prior to initiating thefeeds and adjusting the amount of water later fed to obtain the desiredwater content in the reaction mass. No matter how the water is providedto the reaction mass, the only requirement for the water feed is thatthe proper amount of water be present in the reaction mass duringsubstantially all of the reaction period so that precipitation oftetrabromobisphenol-A occurs as the bromination is proceeding.

In those cases where the amount of water used is in the lower end of therange of about 15 to about 85 wt %, say 15 to 25 or 30 wt %, it may bedesirable in batch operations to add some additional water at the end ofthe bromination of the bisphenol-A and/or underbrominated bisphenol-A tocause additional precipitation of tetrabromobisphenol-A from thereaction mass. In such cases, the added water is counted in the totalsolution water.

The water-miscible organic solvent is preferably fed to the reactor as aconstituent of a solution or slurry of bisphenol-A and/orunderbrominated bisphenol-A. However, if desired, a portion of theorganic solvent can be fed as part of the bisphenol-A and/orunderbrominated bisphenol-A solution or slurry, with the remainingportion, generally a smaller portion, being fed as a separate stream.Also, in the event HBr and/or an oxidant such as hydrogen peroxideis/are to be fed to the reactor, a portion of the water can beintroduced into the reaction mass in the form of aqueous HBr and/oraqueous hydrogen peroxide.

From the above it can be seen that the organic reactant used in thepractice of this invention is bisphenol-A and/or underbrominatedbisphenol-A. The term “underbrominated bisphenol-A” refers to one ormore brominated bisphenol-A compounds in which less than the fourortho-positions relative to the hydroxyl groups are substituted by abromine atom. Typically, the major underbrominated bisphenol-A speciesis the tribrominated species(3,5-dibromo-4-hydroxyphenyl)(3-bromo-4-hydroxyphenyl)dimethylmethane),but one or more other underbrominated species may be present such aseither or both of the dibromo species,3,5-dibromo-4-hydroxyphenyl)(4-hydroxyphenyl)dimethylmethane andbis(3-bromo-4-hydroxyphenyl)dimethylmethane, and/or the monobromospecies (3-bromo-4-hydroxyphenyl)(4-hydroxyphenyl)dimethylmethane.Therefore, the organic reactant fed to the reactor can be bisphenol-Aonly, any one of these underbrominated bisphenols only, any combinationof any two or more of these underbrominated bisphenol-A species only, orany combination of bisphenol-A and any one or more of theseunderbrominated bisphenol-A species. The preferred organic reactant fedto the reactor is bisphenol-A itself. Of course, during the bromination,the bisphenol-A is transformed into various underbrominated bisphenol-Aspecies until it becomes tetrabromobisphenol-A. The same holds true forthe various underbrominated bisphenol-A species which during brominationfinally become tetrabromobisphenol-A. Therefore, the term “bisphenol-Aand/or underbrominated bisphenol-A” in this document refers to theidentity of the compound as it exists prior to being fed into thebromination reaction mass.

As can be appreciated from the foregoing, the manner in which the water,solvent, solution and/or slurry can be fed is not critical to theprocesses of this invention provided that the reaction mass is properlyconstituted. Thus, to simplify matters for discussion, reference is madeto the feed of a solution which comprises bisphenol-A, water andwater-miscible solvent. Such reference is to be understood to mean thatthe water can be fed as a constituent of the solution, as a separatestream or as a combination of both, and that the organic solvent can allbe fed as a constituent of the solution or as a portion in the solutionand as a portion in a separate stream. Also to be considered as part ofthe solution feed is any water or organic solvent which is provided tothe reaction mass as a pre-feed charge or as a part of such a charge tothe reactor. Such reference to the feed of such solution is also to beunderstood to serve in the same way as an illustration by analogy of thefeed of a solution or slurry of one or more underbrominated bisphenol-Aspecies with or without bisphenol-A, water and water-miscible solvent.In short, whatever is illustrated with reference to this particularsolution is intended to apply to the extent possible to analogous feedsolutions or slurries referred to elsewhere in this document.

The water-miscible organic solvent can be defined functionally as amaterial which is capable of solvating Br₂ bisphenol-A,monobromobisphenol-A, dibromobisphenol-A and tribromobisphenol-A underreaction conditions. Further, the organic solvent should besubstantially inert with regard to Br₂, H₃OBr and the ring-brominationof the bisphenol-A to tetrabromobisphenol-A and not contribute to theproduction of troublesome amounts of color bodies, ionic bromides and/orhydrolyzable bromides. Hydrolyzable bromides can include1-bromo-2-alkoxy-2-(3′,5′-dibromo-4′-hydroxyphenyl)propane,1,1-dibromo-2-alkoxy-2-(3′,5′-dibromo-4′-hydroxyphenyl)propane,1,3-dibromo-2-alkoxy-2-(3′,5′-dibromo-4′-hydroxyphenyl)propane, and1,1,3-tribromo-2-alkoxy-2-(3′,5′-dibromo-4′-hydroxyphenyl)propane. Thesolvent, when taken in combination with the water and reactionconditions of the processes of this invention, can have some smallability to solvate tetrabromobisphenol-A, but for the sake of reactionyield, the solvating power should be low, say no more than about 20 wt %and preferably no more than about 5 wt % solvated tetrabromobisphenol-Ain the liquid phase of the reaction mass.

Exemplary of the preferred water-miscible organic solvents arewater-miscible alcohols (e.g., methyl alcohol, ethyl alcohol, n-propylalcohol, isopropyl alcohol, tert-butyl alcohol), water-misciblecarboxylic acids, (e.g., acetic acid, propionic acid), andwater-miscible nitriles, (e.g., acetonitrile). Some water-miscibleethers may also be suitable provided they are not cleaved by the acidicnature of the reaction mass. The more preferred solvents are thealcohols having up to 4 carbon atoms. Most preferred are ethanol andmethanol as they are relatively inexpensive and are easily recovered bysimple distillation techniques for recycle. It is to be understood andappreciated that the organic solvent need not be soluble in water in allproportions at, say, 20° C. Although such total miscibility ispreferable, the organic solvent should at least have sufficientsolubility in water in the proportions and at the brominationtemperature(s) being employed to form a clear one-phase homogeneousliquid reaction medium from which tetrabromobisphenol-A product willprecipitate during the bromination.

The amount of water-miscible organic solvent used is best related to theamount of bisphenol-A fed and can be conveniently expressed as theweight ratio of the organic solvent to bisphenol-A. Typically, the ratiois within the range of from about 1:1 to about 10:1, preferably withinthe range of from about 2:1 to about 10:1, and most preferably the ratiois within the range of from about 3:1 to about 5:1. More or less organicsolvent can be used, provided that the solvent function mentioned aboveis accomplished.

When the water-miscible organic solvent used is ethanol, it is preferredto produce no more than about 4.54 kg (10 lbs) of ethyl bromide per 45.4kg (100 lbs) of tetrabromobisphenol-A precipitate produced.

The Br₂ and solution feed streams are preferably at a temperature whichpromotes process efficiency in view of the desired reaction masstemperature. A suitable liquid Br₂ feed temperature is from about 1° C.to just below the boiling point of Br₂. If the Br₂ is to be fed as agas, then the Br₂ stream temperature should be that which is conduciveto such a feed. For example, such a feed temperature may be within therange of from about 60 to about 100° C. The solution feed temperatureshould be that which does not detrimentally cool or heat the reactionmass or which requires pressure operation so that the feed can be madein the liquid state. If the solution feed is to be made with separatewater and/or organic solvent feeds, then the same comments made abovewith regard to temperature apply to the separate feeds.

The Br₂ and solution and/or separate water, etc., feeds all contributeto the formation of the reaction mass in the reactor. These feeds willproduce a reaction mass liquid phase (liquid portion) and, because ofthe formation of tetrabromobisphenol-A precipitate, ultimately areaction mass solid phase (solid portion). At least a portion of the Br₂feed, be it fed as a gas or as a liquid, will be consumed in thebromination reaction. Any non-consumed Br₂ feed will be found in theliquid phase and, if an oxidant is used, will be joined there by anynon-consumed Br₂ produced by the oxidation of HBr present in thereaction mass.

Preferably, unreacted bromine in the liquid phase of the reaction massis present as the solution is being fed. It is permissible for theunreacted Br₂ content in the reaction mass to disappear for briefperiods of time depending on the level of under-brominated species thatcan be tolerated in the tetrabromobisphenol-A reaction product and/orupon the extent of precipitation of the underbrominated species which isexperienced. In fact, if the period of time is very brief and favorablereaction parameters are chosen, the formation of these underbrominatedprecipitates may not occur to any appreciable extent. It is thusdesirable when establishing the process parameters to be used in a givensituation to observe the process and determine by empirical methods thesensitivity of the chosen reaction conditions to the brief absence ofunreacted Br₂ in the reaction mass. Thus, for the purposes of thisinvention the feature of maintaining in the liquid phase of the reactionmass an amount of unreacted bromine that is in excess over thestoichiometric amount theoretically required to convert the bisphenol-Ato tetrabromobisphenol-A encompasses brief periods of time in which theunreacted bromine content can be nil, but which does not result in theformation of underbrominated species to an extent that results in anunacceptable tetrabromobisphenol-A product, say, one containing lessthat about 96 wt % tetrabromobisphenol-A.

Quantifying for a selected set of operating conditions the preferredtarget amount of unreacted Br₂ to be present in the reaction mass liquidphase is best handled by a trial and error technique. A trial process isfirst defined by choosing an unreacted Br₂ target level and the otherprocess parameters. The produced tetrabromobisphenol-A product from theprocess is analyzed for its tri- and tetrabromobisphenol-A content. Ifthe tribromobisphenol-A level is too high, another trial process isconstructed with a higher target unreacted Br₂ level. The procedure isrepeated until the desired product is obtained. (Note that some benefittowards reducing the tribromobisphenol-A content can also be obtained byusing a higher reaction temperature.) As the chosen unreacted Br₂content gets higher, care should be taken that the unreacted Br₂ contentwill not be so high that it results in the production of tribromophenoland other by-products which are not desirable from a commercialstandpoint. As indicated above, as long as the proposed operation isdesigned so that ample HBr is being maintained in the liquid phase toprotect the tetrabromobisphenol-A against excessive color formation,relatively wide fluctuations in bromine content in the liquid phase toabove about 20,000 ppm and up to about 80,000 ppm, whether intentionalor unintentional, during bromination can readily be tolerated withoutadverse color formation in the tetrabromobisphenol-A product beingproduced.

Quantitative determination of the amounts of unreacted bromine and HBrin the liquid phase of the reaction mass is best conducted by samplingthe reaction mass at intervals during the bromination, removing solidsfrom the samples and analyzing the samples for their contents of bromineand HBr. While the particular methods of analysis used are not criticalas long as they are of suitable accuracy and precision, the followingoverall analytical procedures are recommended:

Determination of Unreacted Bromine:

A weighed aliquot of the clear reaction mass mother liquor (about 1 mLsample) is dispersed into 100 ml of 2% potassium iodide solution. Starchis added as an indictor. Blue color indicates the presence of bromine.The stirred mixture is titrated against 0.01 N sodium thiosulfatesolution to a clear end point. Unreacted bromine is calculated asfollows: ${{Wt}\quad \% \quad {Bromine}} = \frac{\begin{matrix}{{mL}\quad {of}\quad {sodium}\quad {thiosulfate} \times} \\{{Normality}\quad {of}\quad {sodium}\quad {thiosulfate} \times 8}\end{matrix}}{{Sample}\quad {weight}\quad {in}\quad {grams}}$

Determination of Hydrogen Bromide:

A weighed aliquot (about 1 mL sample) of the clear reaction mass motherliquor is mixed with 50 mL of deionized water. About 10 drops of 0.1%aqueous bromocresol green indicator solution is added and titrated with0.5N NaOH solution to a blue end point. Amount of hydrogen bromide iscalculated as follows:${{Wt}\quad \% \quad {HBr}} = \frac{{mL}\quad {of}\quad {NaOH} \times {Normality}\quad {of}\quad {NaOH} \times 8.091}{{Sample}\quad {weight}\quad {in}\quad {grams}}$

As noted above, an important feature of this invention is maintaining inthe liquid phase of the reaction mass, an amount of HBr which willprotect the color of the tetrabromobisphenol-A precipitate from beingadversely affected by the intentional or unintentional variance of theunreacted bromine concentration in the liquid phase to a concentrationin the range of from above about 20,000 ppm to about 80,000 ppm. Byvirtue of this feature, close control of the unreacted bromine contentin the liquid phase is unnecessary—wide fluctuations can be toleratedwithout material adverse consequences such as excessive colordevelopment in the product. Thus continual monitoring of unreactedbromine content in the liquid phase is unnecessary, especially oncesteady state reaction conditions are in place. From then on onlyperiodical monitoring is necessary to ensure that the process isfunctioning pursuant to this invention. Moreover, once the steady stateconditions are in place, the frequency of HBr analyses can be reduced toperiodical checking to be sure that some upset such as line pluggage oretc. has not occurred.

It is possible to estimate the unreacted Br₂ content of the liquid phaseof the reaction mass by the use of colorimetric techniques. A techniquewhich can be used comprises the formation of an acidic (HBr) water andmethanol or ethanol solution. From this solution, several standardsamples are prepared, to each of which is added a different and measuredamount of Br₂. The colors of these sample solutions are then comparedcolorimetrically with the color of the liquid of phase of the reactionmass. A color match is indicative of the amount of Br₂ in the liquidphase. Colorimetric determination for unreacted Br₂ is quite suitable asunreacted Br₂ colors the sample solutions and the reaction mass inaccordance with its concentration. Low concentrations give a pale yellowcolor; intermediate concentrations give a strong yellow color; highconcentrations give an orange color; and the highest concentrations givea dark red color. Unreacted Br₂ concentrations in excess of about 10,000ppm, based upon the reaction mass liquid portion, are preferred,although smaller excesses above stoichiometric can be used. As notedabove, an excess of as high as about 80,000 ppm of unreacted bromine inthe liquid phase can be used although typically the excess will not beabove about 35,000 ppm, with the most preferred amount of unreactedbromine being within the range of from about 50 to about 20,000 ppm.

The unreacted Br₂ concentrations are maintained in the reaction mass solong as bisphenol-A and underbrominated species are likewise present. Ascan be appreciated, the unreacted Br₂ content diminishes as the Br₂reacts, thus, the Br₂ feed acts to replenish the Br₂ in the reactionmass. Using the above-described colorimetric technique, the unreactedBr₂ content of the reaction mass can be monitored during the process andthe unreacted Br₂ content within the chosen target range can bemaintained by adjusting the Br₂ feed, the solution feed or both. Sincethere will be tetrabromobisphenol-A precipitate in the reaction mass,colorimetric monitoring may require that a small stream be taken fromthe reactor and filtered to remove the solids before being submitted toa colorimetric technique. It may also be possible to read the intensityof the reaction mass color without filtration by the use of reflectancetechniques which measure the intensity of the light reflected off of thereaction mass. In all of the colorimetric cases, the color of the liquidphase of the reaction mass can be used as the determinative factor.

It is also to be understood that the method used to obtain the desiredunreacted Br₂ level can be by a method other than the adjustment of thebefore-mentioned feeds. For example, when an oxidant is used to convertHBr to Br₂, the amount of Br₂ generated can be regulated by controllingthe amount of oxidant fed to the reaction mass. The amount of unreactedBr₂ contributed to the reaction mass by oxidation of HBr can besubstantial considering that four moles of HBr are generated for eachmole of tetrabromobisphenol-A produced. Thus, when additional Br₂ isneeded, oxidation of HBr can be used to generate at least a part of theBr₂ needed to obtain the desired unreacted Br₂ level.

With the use of an oxidant to oxidize the HBr to Br₂, the processes ofthis invention can obtain good results by feeding only about two molesor slightly more of Br₂ to the reactor for every one mole of bisphenol-Afed. The other two moles of Br₂ that are needed are provided by the fulloxidation of the co-generated HBr. If there is less than full HBroxidation, then the amount of Br₂ fed to the reactor will be thatamount, in sum with the Br₂ formed by oxidation, which will providequantities of Br₂ which are in excess of stoichiometric. StoichiometricBy for the ring-tetrabromination of bisphenol-A is four moles of Br₂ permole of bisphenol-A. As can be appreciated, when oxidation of HBr is notpart of the process, then the Br₂ feed will be in excess of four molesof Br₂ per mole of bisphenol-A fed.

In a case where both bisphenol-A and underbrominated bisphenol-A, or oneor more underbrominated bisphenol-A species without bisphenol-A are fedto the bromination reactor, the stoichiometric excess of bromine is alsopresent preferably at any given time in the liquid phase reactor. Astoichiometric amount of bromine is one molecule of diatomic bromine(Br₂) for each hydrogen atom present as a substituent in anortho-position relative to the hydroxyl groups of bisphenol-A and/orunderbrominated bisphenol-A fed to the reactor. For example, if the feedwere 1 mole of bisphenol-A and 1 mole of tribromobisphenol-A, therewould be a total of 5 moles of hydrogen atoms in the orthopositions—i.e., 4 moles in the bisphenol-A and 1 mole in thetribromobisphenol-A. A stoichiometric amount of bromine in thisparticular case would therefore be equivalent to 5 moles of diatomicbromine, and pursuant to this invention an amount of bromine equivalentto more than 5 moles of bromine would be fed into the liquid phase ofthe reaction mass, or fed into the liquid phase of the reaction mass andgenerated in situ, or generated in situ. Similarly, if the feed were,say, 1 mole of monobromobisphenol-A, there would be a total of 3 molesof hydrogen atoms in the ortho positions. A stoichiometric amount ofbromine in this particular case would therefore be equivalent to 3 molesof diatomic bromine, and pursuant to this invention an amount of bromineequivalent to more than 3 moles of bromine would be maintained in theliquid phase of the reaction mass. Whatever the manner used in providingthe excess unreacted bromine in the liquid phase of the reaction mass,the amount of unreacted bromine specified above should be maintained inthe liquid phase of the reaction mass.

While on the subject of stoichiometry, it will be understood that forevery atom of bromine introduced into the bisphenol-A or underbrominatedbisphenol-A molecule during the bromination, one molecule of HBr isproduced. In other words, for every mole of diatomic bromine (Br₂) thatreacts with the bisphenol-A or underbrominated bisphenol-A, one mole ofHBr coproduct is produced. Therefore this HBr that is automaticallygenerated in situ should be taken into consideration in designing thefeeds and feed rates to be used in the reaction in order to maintain therequisite amount of HBr in the liquid phase of the reaction mixture.Although most of such coproduct HBr will usually remain in the liquidphase, some HBr may escape into the headspace of the reactor. The amountof such vaporized HBr will depend on such factors as the rate at whichthe bromination reaction is proceeding, the amount of water present inthe liquid phase, the rate of agitation, if any, being used, and thepressure conditions in the reactor. Therefore, in any given situationwhere the conditions for producing and maintaining the particular amountof HBr desired in the liquid phase of the reaction mass during the timethe reactants are being brought into contact with each other so thatbromination is taking place, are not already known, it is desirable toperform a few preliminary pilot experiments in which the calculatedfeeds are adjusted to achieve the optimal conditions for achieving thedesired amount of HBr in the liquid phase of the reaction mass.

Irrespective of the Br₂ source, the stoichiometric excess is desirablesince it is less difficult to control the process by having excess Br₂present at least during most of the reaction period. For batchprocesses, the excess Br₂ present after completion of the process can beremoved by treating the reaction mass with a reducing agent such assodium sulfite or hydrazine.

It is possible to use oxidant materials to generate additional brominein situ in any situation in which this is desirable. The oxidant must becapable of oxidizing HBr to Br₂ in the reaction masses and under theprocess conditions of this invention and without interfering with thebromination reaction. Chlorine in small proportions may be used as theoxidant, but hydrogen peroxide is the preferred oxidant. When and ifusing H₂O₂, safety considerations make it desirable to feed it to thereaction mass as an aqueous solution containing no more than about 90 wt% H₂O₂. Preferred are aqueous solutions containing from about 30 toabout 80 wt % H₂O₂. A most preferred solution is one containing fromabout 50 to about 70 wt % H₂O₂.

Hydrogen peroxide can be fed to the reaction mass at any time. Whenresorting to its use in a batch operation, the H₂O₂ is preferably fedafter most of the Br₂, e.g., above about 50%, has been fed. Forcontinuous operation, the H₂O₂ feed most preferably occurscontemporaneously with at least most of the Br₂ feed. Most preferably,the H₂O₂ feed would start after initiating the Br₂ feed.

Unless the color of the final product is of no importance, the amount ofoxidant fed must not reduce the amount of HBr present in the liquidphase to below the amount necessary for protecting thetetrabromobisphenol-A against adverse color formation in the event ofintentional or unintentional variance of the unreacted bromineconcentration to a concentration in the range of from above about 20,000ppm to about 80,000 ppm. Thus if oxidant is to be fed to the reactor, itcan prove useful to also feed HBr to the reactor in an amount that willensure the presence in the liquid phase of such color-protecting amountof HBr.

Another important consideration in practicing the processes of thisinvention is the reaction mass temperature during the brominationperiod. It is desirable to use a relatively high temperature so that thebromination of the bisphenol-A to tetrabromobisphenol-A will besufficiently fast to reduce the extent of tribromobisphenol-Aprecipitate formation. However, there is a practical limit as to howhigh the temperature can be. For example, temperatures which would causethe production of unacceptable levels of unwanted by-products or thedegradation of the tetrabromobisphenol-A product should not be used.

It is unusual to operate a tetrabromobisphenol-A process at relativelyhigh temperatures, especially when production of a co-product such asmethyl bromide or ethyl bromide is to be minimized. Also, use ofrelatively high temperatures might be expected to complicate the processby increasing the solubility of the tetrabromobisphenol-A in the solventsolution and possibly necessitate a final cooling of, or addition ofwater to, the reaction mass to effect the desired high yieldprecipitation of tetrabromobisphenol-A. The processes of this invention,however, can be operated without excessive coproduction of methylbromide or ethyl bromide, and there is no requirement for a cooling stepto obtain sufficient tetrabromobisphenol-A precipitation.

Operation at relatively high temperatures can contribute to additionalprocess economy and product purity enhancement. Process economy, inpart, can be realized because even at higher reaction mass temperatures,cooling tower water can be used to cool the reactor instead of usingrefrigeration which is required by processes that are operated at lowtemperatures.

Typically temperatures are within the range of from about 30 to about100° C., and preferably are in the range of about 50 to about 100° C.More highly preferred temperatures are within the range of from about 50to about 80° C. These preferred temperatures in the range of about 50 toabout 100° C. and in the range of about 50 to about 80° C. will beutilized during at least about 80%, and preferably, during at least 90%of the time the feeding of the bisphenol-A and/or underbrominatedbisphenol-A to or with excess bromine is taking place, especially whenconducting the process as a batch operation. More uniform temperatureswithin these ranges are typically maintained when operating the processon a continuous basis. However, programmed fluctuations in temperaturewithin these ranges can be utilized in continuous operations, ifdesired. The most highly preferred temperatures are within the range offrom about 50 to about 70° C. Temperatures below 30° C. can be used, butthe organic solvent to bisphenol-A and/or underbrominated bisphenol-Aweight ratio may well need to be high, say from 8:1 to 15:1. For theseratios, temperatures of 30 to 50° C. may be suitable.

The bromination of bisphenol-A and/or underbrominated bisphenol-A is anexothermic reaction as is the oxidation of HBr with H₂O₂. To control thereaction mass temperature, it may become necessary to remove heat fromthe reaction mass. Heat removal can be effected by running the reactionat reflux with the condenser facilitating the heat removal. If it isdesired to operate at a temperature below the atmospheric boiling pointof the reaction mixture, the reaction can be run under sub-atmosphericpressure.

Generally, the basic concepts of the processes of this invention are notappreciably affected by the process pressure. Thus, the process can berun under sub-atmospheric, atmospheric or super-atmospheric pressure.

At process initiation, it is desirable to charge the reactor with aliquid pre-reaction charge which will become a part of the reaction massupon the commencement of the feed. The liquid charge will provide astirable reaction mass and act as a heat sink to moderate temperaturechanges in the reaction mass. The liquid charge is preferably comprisedof water and the same water-miscible organic solvent that is to be fedin the bisphenol-A and/or underbrominated bisphenol-A solution orslurry. It is preferred that the liquid charge be acidic, e.g.,containing from 1 to 20 wt % acid such as HBr₂ HCl, or the like. Theacid seems to promote good color in the initial tetrabromobisphenol-Aproduced. Further, it is preferred that the solvent be saturated withsolvated tetrabromobisphenol-A. It is also preferred that the reactor becharged with seed particles of tetrabromobisphenol-A. The saturation ofthe solvent and the presence of the seed particles both act to enhancethe precipitation of the tetrabromobisphenol-A produced during thebromination period. It is most practical to use a heel from a previouslyrun process of this invention as the liquid charge. Thetetrabromobisphenol-A seed particles can be brought over from theprevious run or can be added separately. If a heel is not available, itis also possible to use a separate water and water-miscible organicsolvent feed, which are a part of the total solution feed, to form theinitial liquid charge. In this scheme, an initial amount of water andwater-miscible organic solvent are fed to the reactor prior to theinitiation of the solvated bisphenol-A portion and/or the slurry ofunderbrominated bisphenol-A portion of the solution or slurry feed. Theonly caveat to this scheme is that there must be apportionment of thevarious feeds making up the solution feed so that there will still becompliance with the various parameters which define the processes ofthis invention.

If the process of this invention is run as a batch process, the Br₂ andsolution or slurry feeds are fed to a stirred reactor until they areexhausted. There is no need for a post-feed cook period of anysignificant length as, under the reaction conditions, the bromination ofbisphenol-A and/or underbrominated bisphenol-A to tetrabromobisphenol-Aoccurs quite rapidly. Also, since the water content of the reaction massis so large and since the tetrabromobisphenol-A is so insoluble in thepresence of such an amount of water, there is only a modicum of benefitin cooling the final reaction mass. The benefit of cooling residesmainly in reducing the vapor pressure of solvated gaseous bromides,e.g., methyl bromide or ethyl bromide, in the reaction mass prior to theliquid-solids separation. There also may possibly be some reduction inrate in the formation of these alkyl bromides. In addition, dependingupon the water content of the reaction mass, cooling may allow foradditional precipitation of tetrabromobisphenol-A from the reactionmass. When operating within the preferred ranges recited herein, theadditional precipitation benefit may not be worth the cost associatedwith obtaining same. Additionally, depending on the separation techniqueused, cooling the reaction mass may make it easier to handle downstreamfrom the reactor. Thus, if none of the above are of concern or relativevalue, then the reaction mass can be subjected to liquid-solidsseparation as soon as it can be transported to the separation equipment.If, however, cooling is desired, the cooling time will depend upon howthe reaction mass is to be cooled and to what temperature it is to becooled. In a laboratory setting, cooling times can range from about oneminute to about thirty minutes.

Additional time may also be used between the end of the co-feed and theprecipitate recovery, if it is desired, to add additional water to thereaction mass at the end of the co-feed to insure that even moretetrabromobisphenol-A precipitate is formed in the reaction mass. Thewater addition and precipitation time can be very short, e.g., less thanabout thirty minutes.

Irrespective of whether or not the reaction mass is cooled or treatedwith more water, it is to be understood that the additional time useddoes not appreciably increase the total amount of tetrabromobisphenol-Aproduced by the process (the total amount includes that which is aprecipitate and that which is solvated in the reaction mass). Theseadditional times, therefore, are not to be considered cook times in thesame way as are the cook times taught for use in prior art processes.

After the recovery of the solids from the liquid, the solids arepreferably washed with a solution of water and the particularwater-miscible organic solvent used in the reaction. The washing removesessentially all the mother liquor from the solids. The mother liquortypically contains impurities such as tribromophenol, HBr₂ andhydrolyzable impurities. A typical wash can be a 30 wt % methanol orethanol in water solution. The washed solids are then rewashed withdeionized water to remove any remaining water-miscible organic solventfrom the first wash so as to minimize emission problems when drying theproduct.

When run in the continuous mode, the reactor is preferably acontinuously stirred tank reactor. The reaction mass is beingcontinuously formed and a portion thereof is being removed from thereactor during the reaction mass formation. The reactor design should besuch that the average residence time in the reactor is sufficient toensure tetrabromination of substantially all of the bisphenol-A and/orunderbrominated bisphenol-A. Terms such as “continuous feed” and“continuous withdrawal” and terms of analogous import are not meant toexclude interrupted feeds or withdrawals. Generally, such interruptionsare of short duration and may be suitable depending upon the scale anddesign of the reactor. For example, since the tetrabromobisphenol-Aprecipitate will tend to settle near the bottom of the reactor, awithdrawal may be made and then stopped for a period of time to allowfor precipitate build-up to occur prior to the next withdrawal. Such awithdrawal is to be considered continuous in the sense that thewithdrawal does not await the completion of the reactor feeds as ischaracteristic of batch processes.

Whether the continuous withdrawal is interrupted or not, the withdrawalresults in a portion of the liquid and a portion of the solids in thereaction mass to be withdrawn together. The solids portion will bepredominately tetrabromobisphenol-A. This mix can be filtered, theprecipitate washed, etc., as is done for the above described batch modecase.

Experimental evidence available to date indicates that in the continuousmode of operation, the preferred reactor residence time should be withinthe range of from about 30 to about 150 minutes when using astirred-tank reactor and the process conditions which are preferred forthat operating mode. Reactor residence time, as used here, is thereactor volume divided by the flow rate at which slurry is removed fromthe reactor.

Product of excellent quality can be produced pursuant to this invention.The tetrabromobisphenol-A product can have a purity of 97 wt % andabove, and with a very small tribromobisphenol-A content, if any, ofabout 2 wt %. Moreover, it is possible to produce tetrabromobisphenol-Aproduct having an APHA color less than about 50 (as determined bydissolving 80 grams of tetrabromobisphenol-A product in 100 mL ofacetone). Hydrolyzable bromides can also be kept low, generally belowabout 60 ppm. The process yields are impressive, with yields within therange of from about 95 to about 99% being possible.

As can be appreciated from the foregoing, the water content of thesolvent, the reaction temperature, and the HBr and Br₂ contents in thereaction mass during the bisphenol-A and/or underbrominated bisphenol-Afeed all contribute to obtaining the desired tetrabromobisphenol-Aproduct in an efficient manner. The selection of particular values foreach of these process parameters to obtain the results desired willdepend on each practitioner's needs and upon the equipment available.One practitioner may emphasize one benefit of using a process of thisinvention over other possible benefits. Thus, that practitioner mayselect different process parameter values than those selected by anotherpractitioner who desires to highlight other benefit(s).

The use of the oxidation of the co-generated HBr to produce a part ofthe Br₂ needs for the processes of this invention may possibly beattractive in a situation where the oxidation is more economical thanthe cost of providing for an equivalent amount of Br₂ in the feed to thereactor. However as noted above, one of the features of this invention,that of maintaining in the liquid phase of the reaction mass an amountof HBr that will protect the tetrabromobisphenol-A from adverse colordevelopment by the intentional or unintentional variance of theunreacted bromine concentration in the liquid phase to a concentrationin the range of from above about 20,000 to about 80,000 ppm, should betaken into consideration in assessing whether or not to resort to suchin situ bromine formation.

Though preferably designed to minimize the production of methyl bromideor ethyl bromide coproduct, the processes of this invention are readilyadaptable to modification to coproduce methyl bromide or ethyl bromide.

While the foregoing descriptions of the oxidation of HBr generally speakof the HBr being oxidized in the reactor or reaction mass, it is withinthe scope of the processes of this invention to also remove HBr from thereactor and oxidize it outside of the reactor (i.e., in another suitableclosed vessel or like apparatus) and then to send the so-produced Br₂back to the reactor, or to separately generate bromine needed for theprocess by operation of a separate installation wherein HBr from one ormore other sources is oxidized to bromine.

When feeding HBr to the reactor, such HBr can be either recycled HBrrecovered from the off-gases of the bromination reaction, ornon-indigenous HBr obtained from other sources, or a combination of bothsuch sources.

It will be apparent from the foregoing description that in conductingthe various processes of this invention it is important during at leasta substantial portion of the time during which the reactants are beingcontacted with each other so that bromination is taking place, toprovide for the presence in the liquid phase of the reaction mass of anamount of (i) unreacted bromine that is in excess over thestoichiometric amount theoretically required to convert the bisphenol-Aand/or underbrominated bisphenol-A to tetrabromobisphenol-A, and (ii)HBr that will protect the color of the tetrabromobisphenol-A precipitatefrom being adversely affected by the intentional or unintentionalvariance of the unreacted bromine concentration in the liquid phase to aconcentration in the range of from above about 20,000 ppm to about80,000 ppm, so that a tetrabromobisphenol-A precipitate of little or nocolor is formed continuously during at least a substantial portion ofsuch time. Since the process can be conducted as a batch process or as acontinuous process, and since various ways and conditions of feeding andoperating can be used, the term “substantial portion” is not an absoluteinvariable fractional number, but rather is to be understood with theapplication of common sense. Simply stated, to achieve the greatestbenefits made possible by this invention one should, to the extentpracticable under the particular set of operating parameters being used,arrange to reach the conditions specified in (i) and (ii) andconcomitant continuous precipitate formation with as little delay as isfeasible. And once those conditions have been reached they should bemaintained as long as is practicable during the bromination. Anadvantage of a continuous mode of operation is that once the steadystate of operation within these conditions has been reached, it ispossible to maintain them as long as is desired. In such case reactionmass and precipitate formed during the start up phases of the operationprior to reaching the selected steady state conditions can be discarded.

The following Examples are presented to illustrate the practice of, andadvantages made possible by, this invention. These Examples are notintended to limit, and should not be construed as limiting, the scope ofthis invention to the particular operations or conditions describedtherein.

The operations described in each of Examples 1-4 were conducted in aone-liter flask equipped with a mechanical stirrer, condenser,thermometer, and a down-drain to continually remove slurry from thereactor. The flask was fitted with a dip tube (⅛ inch O.D.) for feedingbromine vapor, and two feed tubes (⅛ O.D.) which terminated in the vaporphase, for feeding bisphenol-A solution and 50% H₂O₂ solution ordeionized water. The top of the condenser was connected to a vacuumpump. The temperature of the reaction was maintained at 60 to 70° C. bycontrolling the vacuum at about 26 inches of Hg. Bisphenol-A (BPA)solution, bromine and H202 solution or water were fed to the reactorusing uncalibrated peristaltic pumps. The bromine tube from the pump wasconnected to a nitrogen inlet and a bromine vaporizer (a flask heatedwith steam) and a gas outlet connected to the dip tube in the reactor.BPA solution was prepared by dissolving 4000 g of BPA in 4700 g ofethanol and 2000 g of water.

EXAMPLE 1

A 50 wt % solution (200 mL) of ethanol in water was charged to thereactor as the heel. BPA, H₂O₂ and bromine were fed to the reactor atflow rates of about 9.0 mL/min., about 0.9 mL/min., and about 1.8mL/min., respectively. The bromine feed was kept stoichiometricallyahead of the BPA feed, and as a result the reaction mass remained paleyellow. The temperature of the reactor rose to about 60° C. and was keptat that temperature by reflux cooling. The product slurry wascontinually drained from the bottom of the reactor to keep a constantlevel in the reactor. After reaching the steady state, the slurry wasfiltered and washed with 30 wt % aqueous ethanol and then with deionizedwater. The washed precipitate was dried and analyzed. The producttetrabromobisphenol-A (TBBPA) had APHA color of 30 and purity of 98.3%.The mother liquor was found to contain 18.4% HBr and 0.7% Br₂. The ratioof HBr/Br₂ was 26.3.

EXAMPLE 2

The experiment was repeated again using flow rates of about 9.0 mL/min,about 0.9 mL/min, and about 1.8 mL/min as in Example 1. However, in thisexperiment no vacuum was employed, and instead of reflux cooling, thetemperature was maintained at about 60° C. by external cooling of thereactor. After reaching steady state operation, the reaction wasdiscontinued. The isolated product had APHA color of 30 and purity of99.6%. The mother liquor contained 24.4% HBr and 1.6% Br₂. The ratio ofHBr/Br₂ was 15.3.

EXAMPLE 3

In this experiment water was fed to the reactor in place of H₂O₂. BPAsolution, water and bromine were fed to the reactor at flow rates ofabout 9.0 mL/min., about 0.9 mL/min., and about 2.7 mL/min.respectively. The temperature of the reactor was maintained at 60-70° C.by reflux cooling. The slurry was orange due to the presence ofunreacted bromine in the reaction mixture. The product TBBPA isolatedhad APHA color of 50 and purity of 97.4%. The mother liquor had 42% HBrand 3.7% Br₂. The ratio of HBr/Br₂ was 11.4.

EXAMPLE 4

BPA solution, water and bromine were fed to the reactor at flow rates ofabout 9.0 mL/min., about 0.9 mL/min., and about 2.9 mL/min. Thetemperature of the reactor was maintained at 60-70° C. by refluxcooling. As there was significant amounts of unreacted bromine in thereaction mass, the slurry was dark orange. The product isolated had APHAcolor of 70 and purity of 99.0%. The mother liquor contained 49% HBr and7.9% Br₂. The ratio of HBr/Br₂ was 6.2.

It is to be understood that the processes of this invention can be runin combination with processes having process parameters not of thisinvention. For example, if it is desired to produce an intermediateamount of methyl bromide ethyl bromide, a process similar to a processdescribed above using methanol or ethanol as the water-miscible organicsolvent but with process parameters which promote the formation ofmethyl bromide or ethyl bromide, such as, for example, use of a lowwater content in the vicinity of about 10 wt %. This process could berun for a period of time and then could be interrupted with theimposition of the parameters of this invention so as to diminish methylbromide or ethyl bromide production. In this way, the methyl bromide orethyl bromide production can be controlled within desired productionlimits by combining both processes.

As can be appreciated from the above results as summarized in the Table,and when viewed in their broadest aspects, the processes of thisinvention effect the high yield production of a highly puretetrabromobisphenol-A product by providing a reaction system in whichthere is directly formed a tetrabromobisphenol-A precipitate at suchspeed that there is insufficient opportunity for the significantprecipitation of the intermediate, tribromobisphenol-A, while at thesame time not requiring the amount of excess unreacted bromine in thereaction mass to be closely controlled in order to prevent formation ofhighly colored tetrabromobisphenol-A product.

TABLE APHA Color HBr/Br₂ ratio Unreacted Br₂, wt % of Product ProductPurity, % 26.3 0.7 30 98.3 15.3 1.6 30 99.6 11.4 3.7 50 97.4 6.2 7.9 7099.0

This invention is susceptible to considerable variation in its practice.Therefore, the foregoing description is not intended to limit, andshould not be construed as limiting, the invention to the particularexemplifications presented hereinabove. Rather, what is intended to becovered is as set forth in the ensuing claims and the equivalentsthereof permitted as a matter of law.

That which is claimed is:
 1. A process of producingtetrabromobisphenol-A which comprises: a) contacting, during a period oftime, bromine and a continuous or substantially continuous feed ofbisphenol-A and/or underbrominated bisphenol-A in a reaction mass havinga temperature within the range of from about 30° C. to about 100° C. andhaving a liquid phase comprised of a water-miscible organic solvent andwater, in which liquid phase, tetrabromobisphenol-A is relativelyinsoluble; b) during all or substantially all of said period of time,maintaining in the liquid phase of the reaction mass, an amount of HBrwhich will protect the color of the tetrabromobisphenol-A precipitate ind) from being adversely affected by the intentional or unintentionalvariance of the unreacted bromine concentration described in c) to aboveabout 20,000 ppm and up to about 80,000 ppm; c) during all orsubstantially all of said period of time, having in the liquid phase ofthe reaction mass, a presence of from about 50 ppm to about 80,000 ppmunreacted bromine; and d) during all or substantially all of said periodof time, precipitating tetrabromobisphenol-A from the reaction mass. 2.A process of claim 1 wherein the amount of HBr in the liquid phase ofthe reaction mass is, on a weight basis, from about 6 to about 50 timesas much as the maximum amount of unreacted bromine that is expected tobe in the liquid phase of the reaction mass during a).
 3. A process ofclaim 1 wherein the tetrabromobisphenol-A precipitated in d) has apurity of at least about 95 wt % and is present in an amount giving atleast about a 90% yield based upon the amount of bisphenol-A and/orunderbrominated bisphenol-A fed.
 4. A process of claim 1 wherein thetetrabromobisphenol-A-containing precipitate in d) has an APHA color ofabout 50 or less as determinable using a solution of 80 grams of theprecipitate in 100 mL of acetone.
 5. A process of claim 1 wherein theamount of HBr in the liquid phase of the reaction mass is, on a weightbasis, from about 10 to about 20 times as much as the maximum amount ofunreacted bromine that is expected to be in the liquid phase of thereaction mass during a).
 6. A process of claim 1 wherein during at leasta portion of said period of time, the liquid phase of the reaction masshas a presence of unreacted bromine above about 20,000 ppm but not aboveabout 80,000 ppm.
 7. A process of claim 1 wherein during at least aportion of said period of time, the liquid phase of the reaction masshas a presence of unreacted bromine above about 20,000 ppm but not aboveabout 35,000 ppm.
 8. A process of claim 1 wherein the bisphenol in thecontinuous or substantially continuous feed in a) is bisphenol-A.
 9. Aprocess of claim 1 wherein the bisphenol in the continuous orsubstantially continuous feed in a) is at least one underbrominatedbisphenol-A species.
 10. A process of claim 1 wherein the bisphenol inthe continuous or substantially continuous feed in a) is bisphenol-A andunderbrominated bisphenol-A.
 11. A process of claim 1 wherein theprocess is conducted as a batch process.
 12. A process of claim 1wherein the process is conducted as a continuous process, and whereinsaid precipitate is removed from the reaction mass during the continuousor substantially continuous feed in a).
 13. A process of claim 1 whereinsaid water-miscible organic solvent is a water-miscible alkanol.
 14. Aprocess of any of claims 1-12 wherein said water-miscible organicsolvent is methanol or ethanol.
 15. A process of claim 1 wherein saidwater-miscible organic solvent is a water-miscible alkanol; wherein theamount of HBr in the liquid phase of the reaction mass is, on a weightbasis, from about 6 to about 50 times as much as the maximum amount ofunreacted bromine that is expected to be in the liquid phase of thereaction mass during a); wherein the tetrabromobisphenol-A precipitatedin d) has a purity of at least about 95 wt % and is present in an amountgiving at least about a 90% yield based upon the amount of bisphenol-Aand/or underbrominated bisphenol-A fed; and wherein thetetrabromobisphenol-A-containing precipitate in d) has an APHA color ofabout 100 or less as determinable using a solution of 80 grams of theprecipitate in 100 mL of acetone.
 16. A process of claim 15 wherein theprocess is conducted as a batch process; wherein the bisphenol in saidcontinuous or substantially continuous feed in a) is bisphenol-A;wherein said alkanol is methanol or ethanol; and wherein the amount ofHBr in the liquid phase of the reaction mass is, on a weight basis, fromabout 10 to about 20 times as much as the maximum amount of unreactedbromine that is expected to be in the liquid phase of the reaction massduring a).
 17. A process of claim 15 wherein the process is conducted asa continuous process; wherein the bisphenol in said continuous orsubstantially continuous feed in a) is bisphenol-A; wherein said alkanolis methanol or ethanol; wherein the amount of HBr in the liquid phase ofthe reaction mass is, on a weight basis, from about 10 to about 20 timesas much as the maximum amount of unreacted bromine that is expected tobe in the liquid phase of the reaction mass during a); and wherein theprecipitate is removed from the reaction mass during the continuous orsubstantially continuous feed in a).
 18. A process of any of claims15-17 wherein the alkanol is ethanol, and wherein said temperature is inthe range of about 50 to about 80° C.
 19. A process for the productionof tetrabromobisphenol-A, which process comprises: a) feeding to areactor at least bisphenol-A and/or underbrominated bisphenol-A,bromine, water, and a water-miscible organic solvent, to at leastpartially form a reaction mass having a liquid phase containing fromabove about 15 to about 85 wt % water, the wt % being based upon theamount of water and water-miscible organic solvent in the liquid phase;and b) during at least a substantial portion of a), (i) providing forthe presence in the liquid phase of the reaction mass of an amount ofunreacted bromine that is in excess over the stoichiometric amounttheoretically required to convert the bisphenol-A and/or underbrominatedbisphenol-A to tetrabromobisphenol-A, and to continuously form duringsubstantially all of the time the feeding in a) is occurring, aprecipitate comprised mainly of tetrabromobisphenol-A, the yield ofprecipitated tetrabromobisphenol-A during substantially all of the timethe feeding in a) is occurring being at least about 90% based on theamount of the bisphenol-A or underbrominated bisphenol-A or combinationthereof fed up to that point in time, and (ii) providing for an amountof HBr in the liquid phase of the reaction mass which will protect thecolor of the tetrabromobisphenol-A precipitate from being adverselyaffected by the intentional or unintentional variance of the unreactedbromine concentration to a concentration in the range of from aboveabout 20,000 ppm to about 80,000 ppm.
 20. A process of claim 19 whereinat least a portion of the bisphenol-A or underbrominated bisphenol-A orcombination thereof and of the water-miscible organic solvent is fed asa preformed solution, wherein the bromine is fed as a separate feedstream, and wherein HBr oxidant is also fed as a separate feed stream.21. A process of claim 19 wherein the feeds to the reactor include atleast (i) a preformed solution of bisphenol-A or underbrominatedbisphenol-A or combination thereof, water, and water-miscible organicsolvent, and (ii) a separate feed of bromine, and wherein the bromine isfed sub-surface to the liquid phase in the reactor.
 22. A process ofclaim 19 wherein the water-miscible organic solvent is a water-misciblealcohol, carboxylic acid, nitrile, or ether which is not cleaved in thereaction mass.
 23. A process of claim 19 wherein the water-miscibleorganic solvent is an alcohol containing up to 4 carbon atoms.
 24. Aprocess of claim 19 wherein the water-miscible organic solvent ismethanol or ethanol.
 25. A process of claim 19 wherein the reaction masscontains from about 30 to about 85 wt % water based on the amount ofwater and water-miscible organic solvent in the liquid phase of thereaction mass.
 26. A process of claim 19 wherein the reaction masscontains from about 30 to about 70 wt % water based on the amount ofwater and water-miscible organic solvent in the liquid phase of thereaction mass.
 27. A process of claim 19 wherein the weight ratio oforganic solvent to bisphenol-A and/or underbrominated bisphenol-A fed iswithin the range of from about 1:1 to about 10:1.
 28. A process of claim19 wherein the weight ratio of organic solvent to bisphenol-A and/orunderbrominated bisphenol-A fed is within the range of from about 3:1 toabout 5:1.
 29. A process of claim 19 wherein during at least asubstantial portion of a) the reaction mass temperature is within therange of from about 50 to about 100° C.
 30. A process of claim 19wherein the bisphenol fed is bisphenol-A, wherein at least a portion ofthe bisphenol-A and of the water-miscible organic solvent is fed as apreformed solution, wherein the bromine is fed as a separate feedstream, wherein the water-miscible organic solvent is a water-misciblealcohol, carboxylic acid, nitrite, or ether which is not cleaved in thereaction mass, and wherein the reaction mass contains from about 30 toabout 85 wt % water based on the amount of water and the water-miscibleorganic solvent in the liquid phase of the reaction mass.
 31. A processof claim 19 wherein the feeds to the reactor include at least thefollowing two feeds: (i) a preformed solution consisting essentially ofbisphenol-A, water, and water-miscible organic solvent, and (ii) aseparate feed of bromine, wherein the bromine is fed sub-surface to theliquid phase in the reactor, wherein the water-miscible organic solventis methanol or ethanol, wherein the reaction mass contains from about 30to about 70 wt % water based on the amount of water and the methanol orethanol in the liquid phase of the reaction mass, and wherein thereaction mass temperature is within the range of from about 50 to about80° C. during at least about 80 percent of the time the feeding in a) istaking place.
 32. A process of claim 19 wherein during at least aportion of the time the feeding in a) is taking place, the liquid phaseof the reaction mass has a presence of unreacted bromine above about20,000 ppm but not above about 80,000 ppm.
 33. A process of any ofclaims 19, 30 or 31 wherein the amount of HBr in the liquid phase of thereaction mass is, on a weight basis, from about 6 to about 50 times asmuch as the maximum amount of unreacted bromine that is expected to bein the liquid phase of the reaction mass during the feeding in a).
 34. Aprocess of any of claims 19, 30 or 31 wherein at least about 95 wt % ofthe precipitate is tetrabromobisphenol-A, and wherein the precipitatehas an APHA color of about 100 or less as determinable using a solutionof 80 grams of the precipitate in 100 mL of acetone.
 35. A process ofany of claims 19, 30 or 31 wherein the amount of HBr in the liquid phaseof the reaction mass is, on a weight basis, from about 10 to about 20times as much as the maximum amount of unreacted bromine that isexpected to be in the liquid phase of the reaction mass during thefeeding in a).
 36. A process for the production oftetrabromobisphenol-A, which process comprises: a) co-feeding Br₂ and asolution comprised of bisphenol-A and/or underbrominated bisphenol-A,water and a water-miscible organic solvent to a reactor to at leastpartially form a reaction mass having a liquid phase and a solids phase,the liquid phase containing water in an amount of from above about 15 toabout 85 wt % water, the wt % being based upon the amount of water andwater-miscible organic solvent in the liquid phase, the solids phasecomprising predominately a precipitate of tetrabromobisphenol-A; b) thereaction mass liquid phase containing during all or substantially all ofthe time the co-feeding in a) is taking place, an amount of unreactedbromine that is in excess over the stoichiometric amount theoreticallyrequired to convert the bisphenol-A and/or underbrominated bisphenol-Ato tetrabromobisphenol-A, such that during substantially all of the timeof said co-feeding in a), the tetrabromobisphenol-A is being produced ina yield of at least about 90% based on the amount of the bisphenol-Aand/or underbrominated bisphenol-A already fed; c) the reaction massliquid phase also containing during all or substantially all of the timethe co-feeding in a) is taking place, an amount of HBr which willprotect the color of the tetrabromobisphenol-A precipitate from beingadversely affected by the intentional or unintentional variance of theunreacted bromine concentration to a concentration in the range of fromabove about 20,000 ppm to about 80,000 ppm; and d) periodically orcontinuously removing tetrabromobisphenol-A precipitate from the reactoralong with a portion of the reaction mass so that the volume of thereaction mass in the reactor remains substantially constant.
 37. Aprocess of claim 36 wherein the water-miscible organic solvent in a) isa water-miscible alcohol, carboxylic acid, nitrile, or ether which isnot cleaved in the reaction mass.
 38. A process of claim 36 wherein thewater-miscible organic solvent in a) is an alcohol containing up to 4carbon atoms.
 39. A process of claim 36 wherein the water-miscibleorganic solvent in a) is methanol or ethanol.
 40. A process of claim 36wherein the liquid phase in a) contains from about 30 to about 85 wt %water based on the amount of water and water-miscible organic solvent inthe liquid phase of the reaction mass.
 41. A process of claim 36 whereinthe liquid phase in a) contains from about 30 to about 70 wt % waterbased on the amount of water and water-miscible organic solvent in theliquid phase of the reaction mass.
 42. A process of claim 36 wherein theweight ratio of organic solvent to bisphenol-A and/or underbrominatedbisphenol-A in the solution fed in a) is within the range of from about1:1 to about 10:1.
 43. A process of claim 36 wherein the weight ratio oforganic solvent to bisphenol-A and/or underbrominated bisphenol-A in thesolution fed in a) is within the range of from about 3:1 to about 5:1.44. A process of claim 36 wherein the temperature of the liquid phase ofthe reaction mass is within the range of from about 50 to about 100° C.45. A process of claim 36 wherein the bromine is fed sub-surface to theliquid phase in the reactor, wherein the water-miscible organic solventis methanol or ethanol, wherein if said solvent is methanol the reactionmass contains from about 30 to about 55 wt % water based on the totalweight of water and methanol in the liquid phase, and if said solvent isethanol the reaction mass contains from about 40 to about 65 wt % waterbased on the total weight of water and ethanol in the liquid phase, andwherein the reaction mass temperature is within the range of from about50 to about 100° C. during at least about 80 percent of the time theco-feeding is taking place.
 46. A process of claim 36 or 45 wherein theamount of HBr in the liquid phase of the reaction mass is, on a weightbasis, from about 6 to about 50 times as much as the maximum amount ofunreacted bromine that is expected to be in the liquid phase of thereaction mass during the feeding in a).
 47. A process of claim 36 or 45wherein at least about 95 wt % of the precipitate istetrabromobisphenol-A, and wherein the precipitate has an APHA color ofabout 100 or less as determinable using a solution of 80 grams of theprecipitate in 100 mL of acetone.
 48. A process of claim 36 or 45wherein the amount of HBr in the liquid phase of the reaction mass is,on a weight basis, from about 10 to about 20 times as much as themaximum amount of unreacted bromine that is expected to be in the liquidphase of the reaction mass during a).
 49. A process of claim 36 or 45wherein during at least a portion of the time the co-feeding in a) istaking place, the liquid phase of the reaction mass has a presence ofunreacted bromine above about 20,000 ppm but not above about 80,000 ppm.50. A process for the production of tetrabromobisphenol-A product, whichprocess comprises providing a liquid phase reaction system to whichbisphenol-A and/or underbrominated bisphenol-A is/are being fed and inwhich there is being formed a tetrabromobisphenol-A precipitate by thebromination of bisphenol-A and/or underbrominated bisphenol-A with anexcess of bromine over the stoichiometric amount theoretically requiredto produce tetrabromobisphenol-A, and in which there is present duringall or substantially all of the time the bisphenol-A and/orunderbrominated bisphenol-A is/are being fed, an amount of HBr whichwill protect the color of the tetrabromobisphenol-A precipitate frombeing adversely affected by the intentional or unintentional variance ofthe unreacted bromine concentration in the liquid phase to aconcentration in the range of from above about 20,000 ppm to about80,000 ppm, the bromination being conducted at such rate that (i) thereis insufficient opportunity for significant precipitation oftribromobisphenol-A to occur, and (ii) while the bisphenol-A and/orunderbrominated bisphenol-A is/are being fed, tetrabromobisphenol-A isbeing produced substantially continuously in a yield of at least about90% based on the amount of the bisphenol-A already fed, the totalprecipitate formed by the process comprising at least about 95 wt %tetrabromobisphenol-A having an APHA color of less than about 100, saidAPHA color being determinable by dissolving 80 grams of thetetrabromobisphenol-A product in 100 mL of acetone.
 51. A process ofclaim 50 wherein the bromination is performed at a temperature withinthe range of from about 50 to about 80° C.
 52. A process of claim 50wherein the amount of HBr in the liquid phase of the reaction system is,on a weight basis, from about 6 to about 50 times as much as the maximumamount of unreacted bromine that is expected to be in said liquid phaseduring the time bisphenol-A and/or underbrominated bisphenol-A is/arebeing fed.
 53. A process of claim 50 wherein during at least a portionof the time bisphenol-A and/or underbrominated bisphenol-A is/are beingfed, the liquid phase of the reaction system has a presence of unreactedbromine above about 20,000 ppm but not above about 35,000 ppm.
 54. Aprocess of claim 50 wherein the amount of HBr in the liquid phase of thereaction system is, on a weight basis, from about 10 to about 20 timesas much as the maximum amount of unreacted bromine that is expected tobe in said liquid phase during the time bisphenol-A and/orunderbrominated bisphenol-A is/are being fed.
 55. A process for theproduction of tetrabromobisphenol-A, which process comprises: a) feedingto a reactor, bisphenol-A and/or underbrominated bisphenol-A, hydrogenbromide, an HBr oxidant, water, and a water-miscible organic solvent, topartially form a reaction mass having a liquid phase containing in therange of about 30 to about 85 wt % water, the wt % being based upon theamount of water and water-miscible organic solvent in the liquid phase;and b) proportioning the feeds in a) such that during at least asubstantial portion of the time when both the feeding and thebromination of bisphenol-A and/or underbrominated bisphenol-A areoccurring, there is present in the liquid phase of the reaction mass (i)an amount of unreacted bromine that is in excess over the stoichiometricamount theoretically required to convert the bisphenol-A totetrabromobisphenol-A, and (ii) an amount of HBr which will protect thecolor of the tetrabromobisphenol-A precipitate from being adverselyaffected by the intentional or unintentional variance of the unreactedbromine concentration in the liquid phase to a concentration in therange of from above about 20,000 ppm to about 80,000 ppm, tocontinuously form during substantially all of the time when both thefeeding and the bromination are occurring, a precipitate comprisedmainly of tetrabromobisphenol-A, the yield of precipitatedtetrabromobisphenol-A during substantially all of the time when both thefeeding and the bromination are occurring being at least about 90% basedon the amount of the bisphenol-A and/or underbrominated bisphenol-A fedup to that point in time.
 56. A process of claim 55 wherein the hydrogenbromide is fed as aqueous HBr₂ wherein the HBr oxidant is aqueoushydrogen peroxide and the water-miscible organic solvent is an alcohol.57. A process of claim 56 wherein the process is conducted on acontinuous basis and wherein the feeds to the reactor comprise separateconcurrent feeds of (i) aqueous HBr₂ (ii) aqueous hydrogen peroxide, and(iii) a preformed solution of bisphenol-A and/or underbrominatedbisphenol-A, and water-miscible organic solvent.
 58. A process of any ofclaims 55-57 wherein bromine is also fed to the reactor.
 59. A processof any of claims 55-57 wherein the liquid phase of the reaction masscontains in the range of about 30 to about 70 wt % of water based on theweight of the water and water-miscible organic solvent, and wherein theamount of HBr in the liquid phase of the reaction mass is, on a weightbasis, from about 6 to about 50 times as much as the maximum amount ofunreacted bromine that is expected to be present in said liquid phaseduring the time the feeding and the bromination are both occurring. 60.A process for the production of tetrabromobisphenol-A, which processcomprises: a) brominating bisphenol-A and/or underbrominated bisphenol-Aby feeding bisphenol-A and/or underbrominated bisphenol-A to a reactionmass having a reaction mass temperature which is in the range of fromabout 30 to about 100° C., and having a liquid phase, which liquid phasecontains (i) water and a solvent quantity of a water-miscible organicsolvent, the water being present in an amount of from about 30 to about85 wt %, based on the weight of the water and water-miscible organicsolvent in the reaction mass, and (ii) 50 to 80,000 ppm of unreacted Br₂so that a precipitate containing at least about 95 wt % oftetrabromobisphenol-A is being formed substantially continuously duringthe time said feeding is taking place; and b) during substantially allof the time said feeding is taking place, having in the liquid phase ofthe reaction mass an amount of HBr sufficient to protect the color ofthe tetrabromobisphenol-A precipitate from being adversely affected bythe intentional or unintentional variance of the unreacted bromineconcentration in the liquid phase to a concentration in the range offrom above about 20,000 ppm to about 80,000 ppm.
 61. A process of claim60 wherein during at least a substantial portion of the feeding in a),at least a portion of the precipitate is continuously being removed fromthe reaction mass.
 62. A process of claim 60 wherein at least a portionof the unreacted Br₂ in the liquid phase in a) is provided by theoxidation of HBr to Br₂.
 63. A process of claim 62 wherein saidoxidation is effected in situ by introducing an oxidant into thereaction mass to cause oxidation therein of HBr to Br₂.
 64. A process ofclaim 63 wherein said oxidant is hydrogen peroxide introduced into thereaction mass in a water-containing solution.
 65. A process of claim 64wherein during at least a substantial portion of the feeding in a), atleast a portion of the precipitate is continuously being removed fromthe reaction mass.
 66. A process of claim 60 wherein the amount of HBrin the liquid phase of the reaction mass is, on a weight basis, fromabout 6 to about 50 times as much as the maximum amount of unreactedbromine that is expected to be in said liquid phase during the timebisphenol-A and/or underbrominated bisphenol-A is/are being fed.
 67. Aprocess of claim 60 wherein during at least a portion of the timebisphenol-A and/or underbrominated bisphenol-A is/are being fed, theliquid phase of the reaction mass has a presence of unreacted bromineabove about 20,000 ppm but not above about 80,000 ppm.
 68. A process forthe production of tetrabromobisphenol-A, which process comprises: a)brominating bisphenol-A and/or underbrominated bisphenol-A by feedingbisphenol-A and/or underbrominated bisphenol-A to a reaction mass havinga reaction mass temperature which is in the range of from about 30 toabout 100° C., and having a liquid phase, which liquid phase contains(i) water and a solvent quantity of a water-miscible organic solvent,the water being present in an amount of from about 30 to about 85 wt %,based on the weight of the water and water-miscible organic solvent inthe reaction mass, and (ii) at least about 50 ppm but no more than about80,000 ppm, of unreacted Br₂ to continuously produce during at least asubstantial portion of the feeding in a), a precipitate enriched intetrabromobisphenol-A, said tetrabromobisphenol-A being produced in ayield of at least about 90% based on the amount of bisphenol-A and/orunderbrominated bisphenol-A fed to the reaction mass; b) during at leasta substantial portion of the feeding in a), having in the liquid phaseof the reaction mass an amount of HBr sufficient to protect the color ofthe tetrabromobisphenol-A precipitate from being adversely affected bythe intentional or unintentional variance of the unreacted bromineconcentration in the liquid phase to a concentration in the range offrom above about 20,000 ppm to about 80,000 ppm; and c) during at leasta substantial portion of the feeding in a), continuously removing atleast a portion of said precipitate from the reaction mass.
 69. Aprocess of claim 60 or 68 wherein in a) the bisphenol being fed to thereaction mass is bisphenol-A.
 70. A process of claim 60 or 68 wherein ina) the bisphenol being fed to the reaction mass is (i) underbrominatedbisphenol-A or (ii) bisphenol-A and underbrominated bisphenol-A.
 71. Aprocess of claims 60 or 68 wherein the water-miscible organic solvent isan alcohol having up to 4 carbon atoms, wherein the amount of water inthe liquid phase of the reaction mass is in the range of about 30 toabout 70 wt % based on the weight of the water and the water-miscibleorganic solvent in said liquid phase, wherein during the feeding in a),wherein the temperature of said liquid phase is in the range of fromabout 50 to about 100° C., and wherein during at least part of the timethe feeding in a) is taking place, said liquid phase contains in therange of more than about 20,000 ppm but no more than about 80,000 ppm ofunreacted Br₂.
 72. A process of claim 60 or 68 wherein thewater-miscible organic solvent is methanol or ethanol or a mixturethereof, wherein during the feeding in a), the reaction mass temperatureis in the range of from about 50 to about 80° C., and wherein during atleast part of the time the feeding in a) is taking place, said liquidphase contains in the range of more than about 20,000 ppm but no morethan about 35,000 ppm of unreacted Br₂.
 73. A process of claims 60 or 68wherein in a) the bisphenol being fed to the reaction mass isbisphenol-A, wherein the reaction mass temperature in a) is in the rangeof from about 50 to about 80° C., wherein the water-miscible organicsolvent is ethanol, wherein the amount of water in the liquid phase ofthe reaction mass is in the range of about 40 to about 65 wt % based onthe weight of the water and ethanol in said liquid phase, wherein duringat least part of the time the feeding in a) is taking place, said liquidphase contains in the range of more than about 20,000 ppm but no morethan about 35,000 ppm of unreacted bromine, and wherein the amount ofHBr in the liquid phase of the liquid phase reaction system is, on aweight basis, from about 10 to about 20 times as much as the maximumamount of unreacted bromine that is expected to be in said liquid phaseduring the time bisphenol-A is being fed.
 74. A process for protectingtetrabromobisphenol-A against excessive color development during itsproduction by bromination of bisphenol-A and/or underbrominatedbisphenol-A by bromine, which process comprises: a) feeding bisphenol-Aand/or underbrominated bisphenol-A to a reaction mass having during allor substantially all of the time said feeding is taking place, a liquidphase in which tetrabromobisphenol-A is relatively insoluble comprisingwater and a water-miscible organic solvent; b) during all orsubstantially all of the time the feeding in a) is taking place, havingin said liquid phase at least about 50 ppm but not more than about80,000 ppm of unreacted bromine and having the temperature in the liquidphase in the range of from about 30 to about 100° C.; c) during all orsubstantially all of the time the feeding in a) is taking place, havingthe water and said organic solvent proportioned in said liquid phase ata weight ratio within the range of from about 30:70 to about 85:15 thatenables a precipitate containing tetrabromobisphenol-A to be formedsubstantially continuously during substantially the entire time saidfeeding is taking place, and in a substantially continuous yield of atleast 90% based on the amount of bisphenol-A and/or underbrominatedbisphenol-A already fed in accordance with a) up to that time; and d)during all or substantially all of the time the feeding in a) is takingplace, maintaining the relative proportions of HBr and Br₂ in the liquidphase of the reaction mass such that there is present therein an amountof HBr relative to the amount of bromine that will protect the color ofthe tetrabromobisphenol-A precipitate from being adversely affected bythe intentional or unintentional variance of the unreacted bromineconcentration in the liquid phase to a concentration in the range offrom above about 20,000 ppm to about 80,000 ppm.
 75. A process of claim74 wherein in a) the bisphenol being fed to the reaction mass isbisphenol-A, wherein the reaction mass temperature in a) is in the rangeof from about 50 to about 80° C., wherein the water-miscible organicsolvent is ethanol, wherein the amount of water in the liquid phase ofthe reaction mass is in the range of about 40 to about 65 wt % based onthe weight of the water and ethanol, wherein during at least part of thetime the feeding in a) is taking place, said liquid phase contains inthe range of more than about 20,000 ppm but no more than about 35,000ppm of unreacted bromine, and wherein the amount of HBr in the liquidphase of the reaction mass is, on a weight basis, from about 6 to about50 times as much as the maximum amount of unreacted bromine that isexpected to be in said liquid phase during the time bisphenol-A is beingfed.